"Oh, it's not the speed really so much, I just wish I hadn't drunk all that cough syrup this morning" Bill Murrray, Stripes.
I can't believe this one hasn't been mentioned. "A,B,C...Always Be Closing" Alec Baldwin in Glengarry Glenross
"You know we're sitting on four million pounds of fuel, one nuclear weapon and a thing that has 270,000 moving parts built by the lowest bidder. Makes you feel good, doesn't it?" - Sorry...don't remember the character's name from the movie Armageddon (or was that Deep Impact?). Anyway, the line is memorable even if the character/movie was not... "It is the bane of men that they forget" -Merlin (Excalibur)