Ap Shaco is a very versatile build that allows you to harass, and easily get kills from afar and trick your enemies in to traps. In my opinion, Shaco is better suited going AP than DPS.

UPDATES 1/25/12
-Changed Runes
-Added Sorcorer's shoes
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-Added Situational Items
-Fixed some item Order errors

Pros :D
+Very good Harass
+Boxes+AP= good traps
+Clone Explosion does tons of Damage
+Tricky
+He's a DEMON jester Which is pretty Awesome

Cons
-Squishy
- Q is not as useful as AD shaco
- One of the Harder Builds to master
-He laughs A lot.

I take 21/0/9. This helps maximize my maximum ability damage output I take 4 in mental-force. More ability power means more damage early game. Then I take 4 in Sorcery which helps with the cool down of boxes, which you need to be efficient. Then I take 1 in Arcane Knowledge which helps get damage through Magic Resist, 4 In Archmage Which increases yout AP by 5% which is insane! Then Executioner for more damage under low health. For Utility, I take 3 in Expanded Mind which shaco needs because He's pretty mana hungry, then I take 3 in Meditation to expend the amount of times shaco has to go back to base to recharge mana, then 1 point in Good Hands to minimize death time, and of course 1 point in Runic Affinity to increase the duration of buffs which is always good.

I take Exhaust as one of my summoner spells because It has numerous uses with shaco. It can keep enemies in range of boxes to the maximum, slow them so you can catch up with your Deceive, and get in range for that last hit you need to kill a champion with.

I take Ignite You can finish off a champion without having to turret dive or chase them.

Other Options include:
Ghost Ghost can be useful for chasing, but I prefer Exhaust over it because it has many more Practical Uses

Cleanse can be used to escape sticky situations and if the enemy team has a lot of cc

Do not use any other not recommended summoner spells

Backstab Backstab is a useful passive when chasing enemies or deceiving behind them to do extra damage. This is a passive, so you do not level it up

Decieve A great Q ability. It allows you to escape, or catch up to fleeing enemies critting them in the process. I have escaped many clutch situations with Deceive. I take a level at 4, because You probably will be doing more damage with your boxes. I level this ability last because it is the only ability that does not scale with AP, but has its uses in game.

Jack In The Box your main ability to level up. This ability scales well with AP, and best of all Fears enemies, which can be critical in team fights when the opponent team is cc'ed. Although the fear is relatively short, more boxes placed in a location means more damage done during the short fear. You can use boxes to be temporarily wards to check and analyze bushes and monster camps. But note: They do not replace wards

Two-Shiv Poison The best part of this skill is the constant cc that you'll need to keep your enemies at bay. When activated, it throws a dagger which creates a strong slow and damage that can be used to finish off enemies, and to catch up to fleeing enemies. This scales 100% with Ap, so it does extreme damage with A, so I max this out second.

Hallucinate I can't tell you how useful this ulti is. You can use it to trick, harass without taking damage and dealing damage towards your enemies. A good strategy to wear down enemy champions is to hide in a bush, hallucinate, then send your clone out to attack. You want to make your clone look as real as possible, so back away when your clone is taking damage, but be sure to go near them when your clone is about to die so they can take the full blast of the clone's explosion. Hallucenate can also be used to help you survive by confusing enemies making them guess which shaco is actually you (:

I start with a Doran's Ring because it provides shaco with 100 health, (remember how I said shaco is squishy?) and mana regen and some ap. Balanced for Ap shaco. The best part of all is that it fits snugly onto shaco's finger c:

Next, I grab kage's lucky pick, for the extra gold, Ap, and then work my way up to deathfire grasp.

A Fiendish Codex which is OPTIONAL, if you're having trouble building into a deathfire from Kage's Pick.

sorceror's shoes With the Magic Pen it Gives, It is a viable choice for AP shaco

Deathfire Grasp This is probably your main item throughout the game. It gives shaco everything he needs. It gives him 60 ability power, 10 mana regen, A REDUCED COOLDOWN OF 15%, and a Very useful Unique Active which lowers an enemies health by at LEAST 30% of their current health. What else is there to say?

Sheen Sheen gives shaco not only Ability power and mana, but the Passive is great, which is after using an ability, your base damage increases 100% for your next attack! It is a great combo with Deceive and maximizes your damage output.

Lich Bane From your sheen, build your way into Lich Bane. I pick lich bane because not only because of the extra MOVEMENT speed, Ability power, and Mana it gives you, but because of it's passive. Every 2 Seconds, after you use an ability Your base attack gains 100% of its attack. Your Enemies won't know what hit them when this baby is on.

Rabadon's Deathcap Gives the most AP in the Game. It will give you an amazing amount of AP (140), and The most amazing passive ever: increase of AP by 30%! With this, you'll do tons of damage with your abilities!

Void Staff IT gives a decent amount of AP, as well as a good amount of Magic Pen for getting those pesky tanks :p

Situational Items
These Items can be used in specific situations:
Zhonya's Hourglass
This Item is usefully against an ad/ ad carry team (Champions such as Xin Zhao or Caitlyn. it gives you 100 ability power, plus 50 armor do help you survive against those pesky AD carries. Also, the Unique active is the main reason to get this item, which makes you invulnerable to harm, so if you're getting focused, Just pop this baby And you'll be free to continue the fight!

Abyssal Mask if your opponents are building MR and you team has mages, you might want to consider buying this item to help improve your damage output with the -20 MR against enemy champions, and also gives you a decent amount of AP (:

Rod of Ages this is a questional item on it's use on AP shaco. It can improve the survivability of AP shaco, but you shouldn't need it because you have a good escape with your Deceive or your Jack In The Box Nevetheless, If you feel Like you're dying too much or want to be a bit tankier while still gaining ability power, this item is for you.

Mobility Boots I don't really like boots of mobility in AP shaco because it doesn't really help you with his burst damage, but might help you get places faster. If you really feel like you need to get around the map quicker, then pick up these to help you, but Sorcerer's Shoes I think are the better choice

Moonflair Spellblade I think this is an underrated item, and it has its uses in AP shaco. If you feel like that the enemy team has too much cc (for example Lux's Light Binding ) you can purchase this to help you manage if you get hit with one of those snares. +35 tenancy can save your life, plus it gives an ok 50 AP.

Thanks for Reading this Guide, and I hope It helps you improve on your AP shaco Game! (: