Sticking myself with a plasma grenade and running into an enemy(ies) and killing them all. It's a little tough to pull of but it's the biggest WTFLOL thing you can do. That and going titan in UT3 and rampaging a group of enemies, if they overwhelm you and kill you, your body falls over and turns into a time bomb, kills everything (thats not on your team) in a 50m radius, TAKE THAT DIP SHITS!!