a helping hand - 5GP: swap an allies weapon for a Rocket Launcher, Fuel Rod Gun, Sniper Rifle, Beam Rifle or Brute Shot
skewer stopper - 10GP: end a players sword spree
pest control - 5GP: kill 5 drones within 10 seconds of each other
[Edited on 02.06.2012 3:10 PM PST]
-
adrenaline rush - 20GP: touch an unsuspecting elite in the back, when he flinches after seeing you fire dual SMGs point blank at his face [Edited on 10.29.2011 12:43 AM PDT]