If you keep on top of your timers, you will dominate the game, and own the map.

Summoner's Wrath - We pick up this talent because of Ignite. The 5 ability power and 5 attack damage this gives us is greater than 1 ability power from Mental Force .

Brute Force , Deadliness and Alacrity - All of these masteries give us nice sustain in the jungle, quicker jungle clears, and more damage output on our ganks.

Weapon Expertise and Sunder - These talents gives us Armor Penetration, and if you're like me, I can't stand when you have a vast amount of Attack Damage, but still can't touch someone because of their armor. This talent helps us bypass some of that armor, so you get more damage output.

Lethality - Who doesn't love critical hits? I know that I love them, especially when that critical strike is enough to drop someone dead, or finish off a minion before someone else can steal it.

Sorcery- Shaco is highly cooldown dependent. Let's say you're getting chased and you are one second away from Deceive being off of cooldown, but you get killed. These masteries will shorten the cooldown so that doesn't happen to you.

Arcane Knowledge - Shaco's abilities deal magic damage. To help mitigate the Magic Resist that people have, this talent allows our abilities to deal more damage, and possible get the killing blow.

Executioner - This talent can make or break a play. Let's say your team decides to turret dive to nuke down a carry. This talent causes you to do more damage to them as they get lower hp. This could be the difference between getting the kill, or getting killed.
Good Hands - If the enemy team is pushing your turrets and inhibitors after a lucky ace, and they're all low, this talent allows you to revive faster and get back in the game to protect your structures.

Expanded Mind - If you've ever played Shaco, you know that his mana doesn't really last very long early game. This mastery gives us some early game sustain on our mana pool.

Swiftness - Movement speed is always a nice thing to have for Shaco, or any jungle for that matter. Movement speed gives us faster ganks, faster jungle clears, and allows you to backdoor late game.

Runic Affinity - 20% longer duration on buffs. This master is a very nice utility to have due to the mana dependency as Shaco early game. It let's us stay in the jungle longer and clear it out plenty times before we have to go back to the base.