Well, my favorite is "A man chooses; a slave obeys", but since we can't use Bioshock, I'm going to have to go with "Yea verily, though I walk through the valley of the shadow of death, I shall fear no evil, for I am driving a house-sized mass of 'fuck you'." Supposedly something the Mammoth Tanks say in C&C:Tiberium Wars. I haven't played it myself though, so I can't verify that.
Edit: I might change my answer to "Take heart fellow adventurers, for you have curried the favor of Boo, The only miniature giant space hamster in the Realm. My friend and companion ever since my h-h-head wound, he will lead us to victory! Onward to the Gnoll Stronghold to the west! Tarry not! We must go soon!"
This one's from Minsc (and Boo) from the Baldur's Gate games.
Edit 2: Maybe "I grows tired of yelling battle cries when fighting this mage! Boo will finish your eyeballs once and for all so he does not rise again! EVIL, MEET MY SWORD! SWORD, MEET EVIL!!!!" is even better.
Actually fuck it, I'm just gonna go with "Anything Minsc has said, ever." The full list of which is here: http://www.minscandboo.com/quotes.php