I'm unable to provide video links, but some of my favourite:
The desert scene in 'Three Amigos' where Chevy Chase's character ( I think) swills down water for 30 seconds and then ditches the rest, after the other two have shown they have only a drop or sand left in their canteen. From the same movie: "Excuse me: Are you the singing bush?"
Princess Bride: "No more rhyming - I mean it" - "Does anybody want a peanut?"
"In the line of fire" when John Malkovich is testing his pistol at the lake and tells some duck hunters he plans to kill the president, they respond "why would you do that?"- Malkovich responds "why'd you shoot that bird, asshole?" and shoots them.
And lets face it, pretty much all of "Dead man walking" and many other Sean Penn films.