This was created originaly on the official league of legends guides section of the forums, and was only good pre-nerf.

It has come to my attention that my buddys and people that play with me or against me have been asking me to teach them how to play shaco well.
So in this guide i'll be posting my skill path, item build, summoner spells, masteries, runebook and extra thoughts, but I will not be posting his Bio or skill tooltips because I feel that is a big waste of time.

With that being said here is the skill path I have chosen
1.jack in the box
2.two shiv poisen
3.two shiv poisen
4.decieve
5.two shiv poisen
6.hallucinate
7.two shiv poisen
8.jack in the box
9.two shiv poisen
10.jack in the box
11.hallucinate
12.jack in the box
13.jack in the box
14.decieve
15.decieve
16.hallucinate
17.decieve
18.decieve

Quote from Toggle

My top priority is two shiv poisen because its the best skill for any AP harasssment, getting 1 skill in jack in the box and decieve allows me to fear them before two shiving and having at least rank 1 in decieve so i can either chase them down or run away from a gank. Get hallucinate as soon as possible so that its easier to take down golem, and if your skilled enough you can utilize your double to launch devestating harassment on the enemy. If you are not doing well with hallucinate though, here are some tips. click your double and have him run in the direction your enemy is running, most commonly around a tower. the tower kills your double fast and if you played it right, you may just get an early kill. Or you can try it with this method, cast hallucinate in a bush, click the double and have him attack an enemy champion, they will think its the real you, attack it and get bombed.
On another note, after you place jack in the boxes, shiv the enemy when they get close enough to be fear'd, it makes it impossible to escape the turrets attacks. also if you decieve behind the enemy, jack in the box where hes going to run back to his tower, you can shiv him till he reachs your jack in the box, get feared and allow you to throw in another shiv. Another way of utilizing jack in the boxes is to stradegicly place them in the middle alley way of the map(near baron or dragon) to see when the enemy is coming to gank, or to counter gank them.

My item build consists of
regrowth pendant > philosophers stone (Late game sell this for a Haunting Guise)
boots of speed
mejai's soulstealer
sorcerer's boots
abyssal scepter (The Hybrid side of things would suggest you to buy lichbane instead)
zhonya's ring
banshee for survival or lichbane for more damage and speed. (if you already have lichbane, try infinity edge)
sell philosphers stone > get what ever suits you, hp regen, armor, etc.

Quote from Toggle

philosphers stone early game can have a large effect on your gold gain later in the game and give you all the HP/mana regen you'll be needing for the majority of the game. boots of speed because you don't want to spend all your money on sorcerers just yet, with boots you'll have decent speed to chase and retreat. mejai's soulstealer because if your skilled enough, you'll have its passive maxed out on ap before late game arrives. sorcerers boots to keep up with other players speed and make your spells hit harder. abyssal scepter because theres normaly always another anoying caster involved(60 magic resistance against) and the 20 magic pen aura helps you and your teamates significantly. zhonya's ring so that your ap count is at an all time high, and ready to really max out turret damage. banshee only if your having trouble with surviving and they seem to stun you a lot, but if surviving isn't a problem(for a skilled player) get lichbane and get more of those lovely kills. selling philosphers stone, well I rarely get to this point in the game, normaly they surrender by now, but the few times I have gone out this long into a game I got haunting guise.

Summoner spells
Ignite - people really underestimate this spell, at level 18 it deals nearly 500 damage, wich is a lot considering it can save you the trouble of running after someone early to late game. make sure you take your level and calculate the damage ignite will do before you use it, or make sure they have around 100hp or less exactly so that its in the bag.
(off thoughts, make sure they use their heal first before you waste ignite on accident, if you don't know if they have heal or not, go ahead and use it then, they might just forget they have heal.)
Heal - Really I only suggest this to noobs that need healing fast instead of over a period of time, not calling you a noob persay but i'm saying if your a noob shaco.
Rally - if your a skilled player and have rally masteries choose this over heal, it can really boost your ap late game and the healing your team needs to match.

Masteries - 21/0/9(the 9 in utility can be spent in defense, doesn't matter really)
3 deadlyness
1 archmage's savvy
4 sorcery
1 burning embers
1 archaic knowledge
3 sunder
3 brute force
1 improved rally
3 lethality
1 havoc
~
3 perseverence
1 good hands
4 awareness
1 utility mastery

Quote from Toggle

I choose to get things like crit, crit damage and armor pen because even as ap shaco regular hits can often crit and it will slightly boost decieve, burning embers and archaic knowledge will make those shiv hits hard, improved rally ive already explained somewhere, and havoc speaks for itself. the spells in utility are just a slight advantage.

Runebook
Marks 9 "Greater Mark of Insight" +0.95magic penetration each = 8.55!
Seals 9 "Greater Seal of Furor" +0.87Critical damage each = 7.83!
Glyphs 9 "Greater Glyph of Insight" +0.57magic penetration each = 5.13 !
Quintessences 3 "Greater Quintessence of Insight" +1.89magic penetration each = 5.67!
Our Total effect = +19.35magic penetration and +7.83Critical damage!

Quote from Toggle

The reason behind getting all this magic penetration is because it really helps you do full damage with your shiv, and it turns out whenever someone hits the negatives in magic resistance they take Increased magic damage! So try combining this with every other magic pen item in the game and you should manage 79.35magic penetration! assuming you grab void staff and masteries you should be packing an even greater 55% more magic penetration, try eating that tanks.
As for Seals go, I don't really care for small time ability power gain or cooldown reduction for that matter, but the extra 8(rounded off) crit damage with 10%masteries can leave your decieve dealing decent off damage that may help when someones about to run away. That and there aren't any magic penetration seals.

Early game tips
With jack in the box handy, go to any golem spot and post 4 turrets, then lure the golem with an attack to your turrets and post a rally, you may need to post a 5th turret after your 4 are dead. with this buff in hand go forth to your lane may it be top or bottom I don't usualy go mid, post some jack in the boxes strategicly.

Mid game tips
get philosophers stone as soon as possible to maximize its gold gain efficiency and get enough kills to get mejais soulstealer, also try to gank more often to help your team while getting mejai's passive increased. continue to kill golem as much as you can so that you can post jack in the boxes as much as you want.

Late game tips
Utilitze massing jack in the boxes stradegicly so that you can bait enemys into a solo gank. use decieve to run towards their base not the other way around, enemys normaly always go towards your base when chasing you, so if you teleport behind them, they end up running around aimlessly like idiots.

Here are some Screenshots i've put together to give you an idea on were to put those jack in the boxes. http://www.xfire.com/profile/farrisj/screenshots/

Video gameplay
Getting the Golem buff early on in the game -
As blue team http://www.xfire.com/video/18ff37/
As purple team http://www.xfire.com/video/1ab04a/
*Edit*Video gameplay
Any video will be posted on this clans front page, in the videos and screenshots section.

Extra thoughts - Best combos with shaco are pro Fiddlesticks and/or amumu, fiddlesticks offers you double fear and his 16magic pen aura passive, while amumu offers 20magic pen passive on damage and stun/fear. But remember, do not and I cannot stress this out enough, do not duel stealth in any game ever. Learn from experience, if oracles can see jack in the boxes and your decieve, just imagine how useless 2 stealth players would be.
As for my reasons why AP shaco is better then AD, AP deals more damage then AD shaco if pulled off correctly.
AP shaco deals nearly 900+shiv, 1200+hallucinate and 300+jitb damage, going straight to their hp because of magic pen.(you do Increased damage if they hit negative magic resist, taking up to 20% more damage)
AD shaco deals(If you get up to 400attack damage)1000decieve, 400shiv, 600hallucinate, 125jitb, depending on if you have 50% crit damage runebook BUT shiv and hallucinate are reduced by half or more because you have no magic pen, and decieve+auto attacks are reduced by 50% if the enemy has 100+armor and decieves can be dodged.