Maximum gank assassination and snowballing.
Burst damage and target access
Damaging a lot health champion inflicts adaptive damage and harvests a soul form the victim.
Gain a burst of Lethality and Magic Penetration after using a dash, leap, blink, teleport, or on leaving stealth.
Collect eyeballs for champion and ward takedowns. Gain permanent AD or AP, Adaptive for each eyeball plus bonus upon collection completion.
Unique champion takedowns grant permanent out of combat MS.
Empowered abilities and resource manipulation
While above 70% health, gain up to +40 Ability Power or +28 Attack Damage (based on level), Adaptive.
Gain increasing amounts of AD or AP, Adaptive over the course of the game.
+9% Attack Speed
+5 AD or 9 AP
Dark Harvest on Shaco allows you to heavily scale into the mid game for easy one-shot,
Sudden Impact empowers Shaco's damage in ganks when using [Q]. He also makes great use of both the Lethality and Magic Pen thanks to his mixed damage profile.
Eyeball Collection is a great rune choice on champions who rely heavily on early snowball kills and those who build Duskblade for the faster ward-sweeping stacks.
Relentless Hunt on Shaco allows you to cover more ground during the [Q] stealth so that you're able to position perfectly for the kill.
Absolute Focus on Shaco grants you the ability to quickly clear thanks to tanking from [W] boxes as well as the extra damage for ganks.
Gathering Storm on Shaco allows you to massive scale into the late game so that you're able to easily 1v1 and 1-shot anyone.