Hi, im ozo1329 and this is my first guide and it is going to be on shaco the demon jester.
This guide will focus on the 3v3 twisted treeline setting, rather than summoner's rift. Shaco is viable in 5v5s, but please remember that all portions of this guide mostly applies to the 3v3 setting.

Please tell me in the comments about ways i can improve my guide, it will be very much appreciated :)

-btw my computer skills are absolute trash, so i apologize for the lack of images and videos D:

PROS
-Great assassin with deceive
-very mobile
-Great ganker with deceive
-can jungle
-extremely fun!

CONS
-EXTREMELY squishy
-not the best laner
-if he doesnt snowball, he can be useless
-suffers from stealth detection
-some early game mana problems(not a big concern unless you spam him skill like hell)

I take GHOST and IGNITE for my summoners.

-GHOST is used for running, chasing and kiting. When running, combine this with you deceive, and you will get out of almost any situation. When chasing, also combine this with you decieve so you can stay on top of you opponents and just wreck them.
-Note, when chasing with ghost, you can use deceive to get a first hit on the enemy you going to chase, but never use it when chasing unless they either blink/flash or your certain that you can finish them off with 1 hit.

-IGNITE is pretty self explanatory, extra bit of damage to finish off an enemy. If you see an enemy get low, you can deceive in, crit, then throw your shivs, then ignite. (you have slain an enemy)

-Marks
You can take any physical damage amplifiers on Shaco. So attack speed, physical damage, and armor penetration are all good choices on Shaco. Personally, i prefer attack speed because i wont have any attack speed bonuses until i have completed my berserkers greavers, and having a low attack speed wont proc wriggles as much, which shaco NEEDS for him to jungle effectively until higher levels.

-Seals
I take flat armor on Shaco, to compensate for his squishiness early game, also helps with jungling.

-Glyphs
I take flat MR on Shaco, once again to make him less squishy. I take Flat instead of per lvl runes because in 3v3 games tend to have early teamfights so that boost in mr might just help you survive with 50 hp.

-Quintessences
For quints i take armor pen, this helps against high armor opponents until i get black cleaver. You can take attack speed or flat damage as alternatives, if you choose to take armor pen for marks.

I take 21/0/9 for masteries, take all physical attack bonuses in offense, and 9 points in utility for the increase buff duration and that bit of movement speed.

I start with boots, 2 health pots and 1 mana pot. This gives me early mobility to last hit, moving across the map, and staying on top of an enemy when ganking a lane.
Next, i get wriggles lantern. This item is amazing for any jungler as it gives sustain through lifesteal and armor, jungle speed through attack damage and the 425 damage proc, and a free ward.
Then i upgrade my boots to berserkers greavers. This gives me a good amount of attack and movement speed for a cheap cost. I do not take mobility boot, as twisted treeline is a small map and you will be constantly in combat. Also, twisted treeline focuses on early teamfights and heavy damage. Therefore, it is not worth it to waste 650 gold on a bit of extra mobility that you dont need, when you can get 25% extra attack speed for 570 gold.
Next i purchase a bf sword for extra damage, then finally ungrade it into a black cleaver. This item gives a moderate amount of attack damage, some attack speed, but the passive is what make me purchase this item. It shreds 45 armor at 3 stacks, so against non-armor stacking foes, you will be doing almost true damage. (Most of my games usually end at this item)
If the game still hasn't ended, grab a phantom dancer. This item will make you even more deadly, while providing you with utility through movement speed.
IF THE GAME STILL HASN'T ENDED, Get whatever item that suits the situation. LoL is a game of adaptation, so do not stick to this build for all games. Get whatever item that suits the situation. For example, if they have a warwick and he ults you all day, get a quicksilver sash. (i would recommend your either get a banshees veil or a guardians angel as one of your last items, seeing that if the game has dragged on that long, you can't afford to die late game.)

At level 1, take one rank of jack in the box. This helps you to set for your jungle camp(see 'playing Shaco' chapter).
At level 2, take deceive for ganking.
At level 3, take 2 shiv poison.
Then follow this skill sequence hallucinate > deceive > 2 shiv poison > jack in the box

Take hallucinate at level 6,11,16 as it is your ultimate.
I max deceive first to give me a HUGH amount of burst damage, as well been able to use it more as leveling it reduces the mana cost. Decieve can be used to past through ALL walls in Twisted Treeline, making Shaco very mobile and an amazing ganker.
I max 2 shiv poison second as it gives me a moderate amount of ranged damage and extra slow.
I max jack in the box last as most of my opponents run out of range as quickly as possible so it does not do much damage. I also prefer 2 shiv posion's damage and slow over 0.25 sec cc that jack in the box provides. Also, jack in the box can be destroyed by the opponent pretty easily, especially enemys with AoE spells.

This is how i play Shaco in Twisted Treeline. Remember that Shaco's early-mid game is extremely strong, but you must play your early game very well for Shaco to snowball. Once Shaco snowballs, its usually good game, unless your team dies a LOT.

When the game loads, buy your items then rush to top jungle asap. Take 1 rank in jack in the box and start boxing the wolves/wraths buff. Tell your teammates to guard you incase of enemy ganks. When its about 1:40 tell your teammates to move away and back into their lanes. Kill the buff camp, then gank top via the dragon pit. Ping for your teammate to react. Make sure your jack in the box comes off cooldown first, then deceive over then wall, crit, then place a box then start beating on the enemy. If he flashes the wall instantly, dont bother chasing. If he flashes the wall with low health, consider chasing if you think you can catch him.
After the top gank, return to bot lane and farm for a bit. When top returns to lane, gank him over and over again. Your job is to make your top strong and their top useless. Make sure your dont stay in bot too long to take you teammates cs and xp. Go to the jungle and take out the weaker camps.

When you hit 6-7, you should have a few kills, your boots and your wriggles. You should be cruising through the jungle with no problem, taking the buffs and ganking the lanes. You can also go for a dragon kill with your ult. In most cases you can solo it by using your ult to tank it and you hitting the dragon from the back for extra damage. Make sure you drop boxes or wards to cover the ways into dragon to prevent ganks. If your top is free, you can ask him to help.

Level 8-10, you should be doing the same thing as 6-7. Cover your lanes if your teammates have to back, Push with your team and take all the neutrals to give your team a level and gold lead. Also, buy wards! These are some places to ward so reveal lone enemies attemping to take your buffs.
You can gank them while they are jungling and get a couple of easy kills.

Late game(if it even get to that), you should be assassinating people who dare to jungle in your territory. You should be staying at the back before teamfights start, as you can do

Quoted:

A TON OF DAMAGE

but you are also very squishy. Remember, NEVER EVER deceive into a fight until you are sure they won't all turn and focus you. Leave deceive for last hit/chasing/escaping.

This may not be necessary but its a personal habit of mine. I buy lots of potions when i go back to base, because of Shaco's tiny little health and mana bar. You may live through an encounter with an enemy just because you poped a health potion before you started fighting. Mana potions will also save you/net you a kill in some situations. If you are oom and you get caught, you are just going to die. If you activated a mana pot, you can stall long enough for you to get just enought mana to deceive and laugh in your enemy's face. Potions also help you stay on the map for as long as possible, so you don't have to base often. I would recommend you to buy at least 2 health potions and 1 mana potion when you go back to base.

Long story short-potions are good for Shacos :P

This has been ozo1329, bringing you my way of playing Shaco on Twisted Treeline. I hope you guys leave some constructive feedback on what i did right, what i did wrong. Thanks for viewing guys :)

Bai X.X

-due to the recent... 1 day after the release of my guide 'SEJUANI patch', Shaco's jack in the box has been nerfed in the way that they can only stay on the map for 60 seconds instead of 90.
This might make it difficult to box the neutral camp in the beginning, you can ask your top teammate to help a bit, but make sure he doesn't steal any xp as it requires all 3 neutral monsters for you to reach lvl 2.