When you play a weapon on one of your units, that unit gets Berserk.
Card sounds may differ from in-game as they get updated.
Quickdraw - Units with Quickdraw kill blockers before they can deal damage back. Note that Quickdraw only works while attacking, not while blocking.
Berserk - Units with Berserk can make a special double attack one time: If it survives the first round of battle, it will attack again. This can only be used once, and gives the unit Reckless.