Add a new power-up that, if you say "Go 0 blood to $(player_name)'s legs/arms/head" while it's in effect, makes the following happen to the player you curse:
Legs - move slower.
Arms - more spread.
Head - aim moves randomly.
Huh? "Say", as in a chat message?
..and during the time spent on typing ''Go 0 blood to $The Player With The Unnecessarily Long Name's legs/arms/head" this player will kill you without hestitaion.
Great idea.
Yeah, people will make sure you can't autocomplete their name by using unicode, and you're screwed. Also fakenickers.
To be honest, what would be the benefit of this? A new powerup that has a noncontrollable effect to players you may even can´t see? This sounds for me like a killstreak reward from CoD:MW2 which pretty much breaks the gameplay. Just my two pennies...