Hello Mobafire, This is my first build that I will be submitting. Any constructive feedback would be greatly appreciated. This first guide is rather wordy and not all too visually appealing but it covers just about everything I know about Shaco. Hope it helps.

Shaco is an incredibly fun champion with all sorts of interesting tricks that makes him a difficult but rewarding hero to play. Shaco is by no means a perfect champion however, he is very squishy so when and how you engage is very important. Enemies with oracles will be able to also see you while in stealth, and see your box nest ahead of time, leading to complications.
With plenty of practice, you can get a feel for Shaco's strengths and weaknesses, so all that is left is an item build. Shaco is typically built either ad jungle or ap lane, both having different advantages and disadvantages.

Ad builds are the most popular as his Deceive can proc for godly damage, followed up by auto attacks that slow thanks to his shiv passive(assuming it is off cooldown), allowing Shaco to slice and dice anybody to little pieces in no time flat, with little chance for escape. The disadvantage is a lot of ad builds recommend numerous high end items such as infinity edge and triforce that require more gold then you will realistically be able to accumulate though the course of an average game. Since Shaco now typically starts in the Jungle, it is hard to develop a solid cs as you should be roaming the jungle grabbing buffs and ganking lanes in the early phase.

Ap builds are more for laning, and for a burst damage hit and run style of play. The fun with Ap builds is that your shiv will harass for meaty damage, and with the low cooldown and low mana cost you can periodically use your shiv to harass enemies, forcing them back and denying the enemy gold and hopefully exp. Your boxes will also do great damage and can even get you first blood if you start stacking in your lane brush at level one. Seeing an enemy face-check a brush you just loaded with boxes is priceless.
Ap builds while having incredible burst damage will be forced to rely on lots of tricky positioning and baiting to get enemy players to chase you into boxes. More experienced players will be wise to your tricks and you will be forced to shiv harass all day as they won't fall easily into your trap nests. Your Q also suffers, with very little damage early and mid game.

The last problem I see in Shaco is lack of team fight potential.
While an incredible assassin that can easily 1v1 most champions, he has a hard time getting into a good spot in a team fight. You either have to wait for the enemy to use up all their crowd control skills on a different person, or wait for somebody from your own team to initiate the fight.

My goal with this guide was to facilitate the following:
1. Find a relatively cheap build that still provides a lot of damage.
2. Focus a little more hybrid so that Shaco can get the most out of all his skills.
3. Empower his clone so that it is more then just a walking bomb or juke assistant.
4. Find something that Shaco can do that also helps his team in fights.

Gentleman may I present to you: Shaco the Skin Flayer.
By utilizing attack speed and items that shred armor and magic resistance, you will make your enemies much more vulnerable to your allies as well as yourself. Once more, these stacks can be applied by your clone, doubling the speed of supplicating the debuffs to the enemy. With near maxed out attack speed with these items getting in all the necessary hits in on an enemy will take only moments. This build is theoretically useful for countering the offtank metagame.

I go standard jungle runes using armor pen reds and quints and flat armor yellows. You may use your choice blue depending on how you play, either with lower cooldowns, added magic resist, or more attack speed for a faster jungle time.

I focus on a 21/0/9 build which speeds up jungle time and maximizes damage which you will want when you gank lanes.

Wiggles Lantern: A very powerful early game item that will not only help you clear the jungle faster, but also provide you with a very important ward which I recommend you keep on dragon for most of the early game. If the enemy team has a lot of high hp champions, you may want to consider building bloodrazor instead, using the vamp scepter in the gunblade as apposed to wiggles. This is highly situational however and much more expensive so plan accordingly.

Mercury Treads: I feel the tenacity and magic resist are honestly too good to really go with anything else. Shaco is very vulnerable to CC, and being able to deceive away sooner after a gank attempt on your life makes all the difference. This is all a matter of opinion however and if you like you can also go Boots of Mobility or Boots of Lucidity as alternatives. Do not go Berzerker's Greaves unless you plan to sell it later as you won't really need the attack speed from those boots.

Malady: A very cheap item, but also incredibly deadly in the right hands. Malady will help you deal an extra 20 magic damage per hit but the real advantage of using this item is shredding the target's magic resist. You can reduce up to 24 MR which is the equivocal of erasing somebodies glyphs of Shielding at level 18, after just 4 hits. This item is going to make your shiv hurt, I mean really hurt, not to mention your boxes and your clone's explosion damage. Speaking of the clone, by using your ult, you will only need to place two hits a piece on a champion to get the max mr reduction. The debuff will last for 8 seconds, but auto attacking will reset the duration.

Black Cleaver: The armor shredding equivalent of Malady, but much more powerful. In 3 hits you will reduce the enemies armor by 45 for 5 seconds. You can take advantage of this with your deceive, but the debuff is really more for your ad carries to take advantage of.

Wit's End. A very powerful item that now also provides magic resist. You can use the added 50 MR but what is really nice is the 42 damage per hit you receive with this item. With your clone you will now do a bonus 84 damage when both you and your clone attack. Considering your attack speed, you will rapidly chip away at your enemy's hp while hopefully nullifying enough magic damage to allow for an escape when needed.

Hextech Gunblade: This item seems a little out of place at first but consider the following.
Ad and Ap which will help scale all your abilities, particularly your shiv which takes a ratio from both. Life steal and even spell vamp, meaning your boxes and shiv will now heal you for a portion of the damage done. And the active which can act as an extra nuke and soft cc ability. If you are having a hard time remembering to use your active, try rebinding the keys to use your first and second items slots as 'a' and 's'. You can now treat your items as though they were extra summoner spells.

Guardian Angel: Most games will not even last long enough for you to complete your Gunblade, but in the situation that the game does last that long, sell your wiggles for a Guardian Angel so you have enough survivability for late game team fights. As Shaco you should be constantly stalking battles, engaging at the right time to do as much damage as possible, and then back off before the enemy team can retaliate. When team fights get crazy however, you may end up finding yourself at the thick of it all, taking chain CC spells and possibly dying. If you do die all hope is not lost, your q should be off or nearly off cooldown by the time you revive, giving you a chance to escape and reengage the enemy at your digression. Having GA also has a powerful mental game behind it, making enemies not want to focus you as you will just revive and give your team the chance to initiate. If you have enough gold, and the passive is down for GA, you can sell it and rebuy it, completely ignoring the CD for the item.

Don't forget to buy elixirs, they really do help, they also make you really shiny.
Buying an oracle of your own is not a bad idea either, allowing you to see any wards the enemy might have placed and denying them map awareness.

Now for some Optional Items.

Bloodthrister: If you are aiming for raw AD damage, step no further then this incredible item. For 3k you get a potential 100 ad with massive lifesteal. Don't bother if you find yourself dying a lot however, the stacks are what make this item really hurt. Substitute for Gunblade or if you got the money, get the Gunblade and lose the Malady instead. Because if you are buying a bloodthrister, you probably are not focusing ap.

Triforce: Expensive but also everything Shaco needs in one item. Simply having this item will make Shaco feel more responsive due to the extra move speed, and the passive 150% damage after using a spell really synergies with your Q, allowing you to use your Deceive for some real damage and initiation. Another possible substitution for Gunblade if you are simply not a fan but I would personally lose the Malady as again this is more of an AD item.

Hexdrinker: If casters are keeping you underfarmed, then you will need this. It will give you the AD you need until you can focus on cleaver, but also provide you with plenty of mr and a passive shield protecting you from magic damage when you are low on hp. It is cheap, the cooldown is under a minute, and the shield may very well save you long enough to get the hell out of there. Synergies real well with Wit's End and Merc Treads, giving you incredible magic resist without having to resort to buying a purely defensive item.

Banshee Veil/Randuins: Both possible substitutes for GA if you are not a personal fan. One is for caster heavy CC teams, while Randuins is for countering AD carries that try to focus you. If you are building Randuins, go ahead and build the heart of gold early on for the gold/10 and extra HP which Shaco really needs.

My skill sequence focuses on getting your shiv to level 5 as quickly as possible while getting your box to do decent damage as well as fear for a longer duration. You will use Q to initiate but be aware that it won't be doing a whole lot of damage until you build some AD.

Proper utilization of your Deceive will be very important, as it can blink over walls, and provides you with invisibility. This will be your main initiation and juking tool.

Where you place your boxes is also important, try to place them at high traffic areas, particularly in brushes as the box will help provide vision. You can stack boxes directly on top of each other, maximizing the amount of damage the stack will do when activated. This is called a box nest, and while powerful is not something you want to focus on for to long as your boxes have very long cooldowns to start with. Making nests are much easier later in the game if you build cdr or have blue buff. You can also place boxes a short distance away from each other in a jagged 'landmine' formation, causing them to activate individually. This is more useful if your goal is to fear the enemy over a longer duration, keeping them preoccupied. Typically however use your boxes simply as wards, to keep track of enemy positions.

Your shiv is a high damage nuke that scales off of both ad and ap. it also provides a slow, either though using the skill on an enemy, or using your auto attack while the ability is off cooldown. compared to your other skills, it has a low mana cost and low cooldown, making it great for harassing enemies. Try to focus on auto attacking the enemy and only use the shiv when the enemy is out of range for you to hit them or if the shiv will do enough damage for the kill. This will ensure you have used the slow to its maximum extent. This is particularly important when it comes to your clone, if your clone can't catch up to land auto attacks, then the clone might as well be useless.

Your ultimate is very powerful but also very difficult to use correctly. It is basically creating a second you that takes increased damage and does a percentage of your damage. When your clone dies, it will explode and do large ap aoe damage over a small area. This guide seeks to get the most out of your clone by utilizing on hit effects which the clone can use. To control your clone, simply hold alt and right click. The clone will attempt to target the same enemy you are attacking should you simply right click, which most of the time you want. If you can help it, try not to let enemies see you ult, instead use it out of the enemies field of vision, have the clone walk out in front with you still hidden, and shadow your clone. Once you find a target, initiate by having the clone go first, then deceive in and strike the target from the back. Remember that people can tell really easily which one is real if you happen to have a buff on you, since the clone doesn't get the jungle buff animation. You can also use your clone to tank towers though it will only take so many shots before dying. If you are in a teamfight with low hp and your ult is up, try ulting and immediately deceiving away somewhere close but out of view. Have the clone attempt to run away from the fight as though it was you, and if done correctly the enemy will attempt to focus down the weak Shaco, only to have it explode in their face for massive damage.

Never forget your passive either, an extra 20% damage from striking an enemy from the back. This shouldn't be too hard as Shaco excels at chasing down enemies that may attempt to flee. This applies to everything so use your boxes in the jungle to help you hit creeps from the backside, increasing damage and therefor decreasing jungle time.

Smite is a must have if you are in the Jungle, it speeds up jungling time, as well as allowing you to potentially steal dragon and baron from the enemy team if you can catch them off guard at the right moment.

Ghost is a great spell to have a Shaco, as he can activate the spell, deceive in, and get into position to gank incredibly quickly. Catching people off guard is crucial to success and the extra speed helps you pull this off by allowing you to get into position better during your stealth.

Exhaust and Flash are viable but I don't feel they are needed nearly as much.

There are many videos and guides on proper Jungle routes, but I will describe my own method as well.

Start at blue, stacking boxes far enough away that they won't activate immediately when blue spawns, but not too far away as you need to drag the blue golem into the trap nest. At 1:46 stop placing boxes, when the golem comes up, strike the golem and pull it into your nest. Ideally you do not want the boxes shooting the little lizards and exclusively focus on blue. If you managed to get over 4 boxes down before 1:46 then you should be able to take blue without even using smite. It is important you stop placing boxes at 1:46 because you will need the ability off cooldown as you will place one last box behind the blue golem while the initial nest does it's thing. The goal with jungling is always take as little damage as possible, and clear the camps as quickly as you reasonably can. Go to wolves, then wraiths. Smite the blue one and kill off the little wraiths. Now that you are lvl 3 we will get another point it boxes to speed up taking red which you will take after small golems. Just repeat what you did at blue except now you only need around 3 boxes and smite. You are now level 4 with both buffs and ready to gank. Blue isn't as needed to gank a lane but it helps, the real buff you want to grab is red, for the slow and burn damage. Do not gank a lane without red as it will most likely turn out unsuccessful.

Prioritize ganking mid if you can, but focus on helping the lane that is pushed back the most. If your team has everything under control, then continue to jungle while warding the river with boxes to help prevent ganks from the enemy jungler if they have one. And while it might seem a little silly at first, learn to verbally communicate your plans to your teammates, or at least use a ping to catch your team's attention. For a gank to really work you need your teammates doing their part in the attempt, if you attempt a gank without saying anything then your allies might not be ready to receive you, only noticing you moments before or even after you initiated. Besides, people really like it when their teammates show that they want to win are are willing to act like team players to do it. Simply communicating will help you win games.

This is still a highly experimental build that I will need to play around with, and I will have to update the guide to be more appealing as time goes on.

I did enjoy writing this however, and I hope it helps you find the most appealing way to play Shaco for yourself.

If nothing else remember this:
Be creative
Be unpredictable
Be Shaco
Spread chaoS.

Now go out there and flay the enemy.