"It wasn't Han or Greedo. It was me who shot first!"
In response to Black Ops' tendencies during online multiplayer to declare my death and my opponent's victory, even though I totally shot first. And then it shows me a historically-inaccurate Killcam replay where I apparently didn't even raise my rifle and my opponent emptied an entire magazine into me.
Also, during Halo Reach:
"STOP MOVING!"
"It's like every Elite is played by Bruce Lee!"
^The former is the way I react when an Elite just happens to move at the exact moment I lined up a sniper bullet to his head, because, while I'd never expect an enemy to flat-out hold still for a sniper, the Elites in this installment of the series all move around a little too much like they're stepping on hot coals or something. The second quote is something I said at least once when an Elite ran up to me and insta-killed me with a boot to the head. No seriously, they learned to kick when they fight.