Plenty of awesome quotes in Planescape Torment of course. The above link is just awesome :-)
I also like some from Mass Effect 1&2 :
Urdnott Wrex: So this is the famous turian general? How did your kind ever defeat us?
General Septimus: I may be drunk, krogan, but you're ugly. And tomorrow I'll be sober.
Tali'Zorah nar Rayya: How can you fight your own people?
Urdnott Wrex: Anyone who fights us is either stupid or on Saren's payroll. Killing the latter is business. Killing the former is a favor to the universe.
Urdnott Wrex: Just because I like you doesn't mean I won't kill you.
And just too many others... here are the links :
ME1 ME2 And of course, from Freespace 2 :
"Dive dive dive ! Hit your burners pilot !" splat.
Lt. Cmdr. Christopher Snipes: Outstanding job. Most pilots fly only one suicide mission.