Rock On lets a thrown rock stun weaker enemies, which sets them up for a stealth kill. It is a Tier 4 Melee skill that turns the rock you always carry into a quiet opener.
It is a good pick for stealth players. If you go loud, other Tier 4 skills give more.
Thief In The Night and Escape Artist. Quiet approach, stun, then a kill without a fight.
Aim at a lone target near cover. The stun buys time but not much, so throw from close range.
Bull Rush
Lets a sprinting melee attack stun a regular human or a Swarmer.
Busted Up
Restores some stamina with each melee kill.
Escape Artist
Lets you kill a smaller enemy right after breaking out of its grapple.
Executioner
Lets you stealth attack heavy Freakers, and kill heavy Freakers or large animals when breaking a grapple.