Most would say that death isn't funny. It isn't, unless you're Shaco - then it's hysterical. He is Valoran's first fully functioning homicidal comic; he jests until someone dies, and then he laughs. The figure that has come to be known as the Demon Jester is an enigma. No one fully agrees from whence he came, and Shaco never offers any details on his own. A popular belief is that Shaco is not of Runeterra - that he is a thing summoned from a dark and twisted world. Still others believe that he is the demonic manifestation of humanity's dark urges and therefore cannot be reasoned with. The most plausible belief is that Shaco is an assassin for hire, left to his own lunatic devices until his services are needed. Shaco certainly has proven himself to be a cunning individual, evading authorities at every turn who might seek him for questioning for some horrendous, law-breaking atrocity. While such scuttlebutt might reassure the native inhabitants of Valoran, it seems unimaginable that such a malfeasant figure is allowed to remain at large..

Whatever the truth of his history might be, Shaco has joined the League of Legends for reasons only he knows. He is a terrifying figure, typically shunned by both his fellow champions and the media at large. Only the summoners in the Institute of War know why such a creature was allowed into the League, but most Runeterrans suspect it to be a means that allows the power that be to keep an eye on the ever-elusive Shaco. Unsurprisingly, this champion is popular in places where madness can openly reign, such as among the power-hungry summoners of Zaun and Noxus.

Whatever you do, don't tell him you missed the punch line

Abilities
Deceive - Shaco stealths himself instantly and teleports to target location. His next attack is guaranteed to critically strike.
Shaco teleports nearby and becomes stealthed for 3.5 seconds.

His next basic attack within the next 6 seconds will critically strike, dealing 140/160/180/200/220% damage (normal critical strikes deal 200% damage).

Cost
90/80/70/60/50 Mana
Range
500

Jack In The Box - Shaco creates an animated Jack-in-the-Box at target location, which will wait, stealthed, to Fear nearby units and attack them when some come nearby.
Shaco creates a Jack in the Box at the target location. It will Stealth after 2 seconds, and pop out when an enemy comes near, fearing nearby enemies for 0.5/0.75/1/1.25/1.5 seconds and attacking them.

Its attacks deal 35/50/65/80/95 (+0.2) magic damage and it lasts for 60 seconds while stealthed or 5 seconds while firing.

Cost
50/55/60/65/70 Mana
Range
425

Two-Shiv Poison - Shaco's Shivs passively poison targets on hit, slowing them and applying a miss chance to minions. He can throw his Shivs to deal damage and poison the target.
Passive: While Two-Shiv Poison is ready to cast, Shaco's basic attacks reduce the target's Movement Speed by 20/22.5/25/27.5/30% for 2 seconds. Also reduces minions' chance to hit by 20/22.5/25/27.5/30% for 2 seconds.

Active: Deals 50/90/130/170/210 (+ ) (+1) magic damage to target enemy and reduces their Movement Speed by 20/22.5/25/27.5/30% for 3 seconds.

Cost
50/55/60/65/70 Mana
Range
625

Hallucinate - Shaco creates an illusion of himself near him, which can attack nearby enemies. (Deals half damage to turrets.) Upon death, it explodes, dealing damage to nearby enemies.
Shaco vanishes briefly and reappears with a clone that lasts up to 18 seconds. The clone deals 75% of Shaco's damage and receives 50% increased damage.

On death, the clone detonates, dealing 300/450/600 (+1) magic damage to nearby enemies.

Cost
100 Mana
Range
500

Backstab - Shaco deals 20% bonus damage when striking a unit from behind.

Tips

Using Deceive over terrain can help you make a clean escape.
Try getting items with on-hit effects. These will also benefit your Hallucination clone.
Deceive's damage can be increased with increased Critical Damage effects like Infinity Edge

Deceive into combat as and initiation.

If enemy champion begins to run use "e" to range them and slow their movement speed.

To increase damage, and confuse enemy, it is beneficial to use "r" at the beginning of a gank.

To maximize AD, (Attack Damage), I selected runes such as the greater mark of strength to add almost an extra 10 damage, which is beneficial early game.
Also I add Greater Seal of Malice to increase critical strike chances by ~4% which stacked with infinity edge can deal 250% of your normal attack damage, which for all of you who are looking at overall damage at max potential is critting for almost 900 damage a swing.
I use Greater Glyph of Alacrity to increase my attack speed by an extra 6% which is very helpful in certain situations.
I use Greater Quintessence of Malice twice to increase my crit chance by an extra 3 1/2% which makes the basic crit chance start out at 7%.

Pros
Good Initiator
Insane Attack Damage
Good Early Game
Quite simple to follow
Great Life Steal/Crit Chance
Fun to Play
No need for leash if you decide to use smite instead of Ignite

Cons
Most tanks are going to be hard to kill.
Stuns are very affective against Shaco

With a build like this, Shaco will do insane damage, and will be great to initiate attacks, especially when opening with Deceive, because it garuntees a critical strike on next hit.
Initiate, then run back behind your tank, wait for the other team to open up on your tank, and then jump back in with another deception, and use your "e" skill whenever it is up, it'll deal insane damage, and slow enemy movement speed just as well as your auto attack.

For those of you who are asking why is there a 2nd stack of phantom dancers in there at the end, it is simply because you sell your boots and then equip phantom dancers, you lose a little bit of movement speed, but you gain crit chance, and attack speed.