Deal 7% more damage to low health champions. Gain AD/AP after kills or assists.
Electrocute is a great rune for Shaco's natural high-burst assassination playstyle, allowing you to pipck up quick early kill and snowball.
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.
The bonus Attack Speed empowers Shaco's ability to quickly clear the jungle for early ganks. It also empowers the damage of your ganks by allowing you to get off an extra auto attack or more during your combo.
WhyCoup De Grace
Coup De Grace is the go-to assassination rune for those champions (like Shaco) who rely heavily on blowing up squishy backline champions.