This one is obvious.
Yippee Ki Yay, Motherfucker.
I'm lucky this was on cable one night while I was solidifying/pondering the list. I had forgotten about just how great the scene is. The line itself becomes little but a catch phrase when separated from the rest of the scene, but in context of the conversation, it's absolutely perfect.
YouTube only has this short version, but there's an IGN countdown (a countdown of classic movie scenes, ironically enough) that has a more extended version.
And, as an added bonus, because it is one of the truly great TV edits, this comes from Die Hard 2: Die Harder in an Airport