I can think of tons of them, but this one came to mind today when I was talking to Lisa about sitting on the porch having a cigar tonight.
Robin Williams - Elmer Fudd does Bruce Springsteen
That skit comes to mind a lot, and it never fails to make me laugh. When I looked it up at Youtube and started playing it, I laughed out loud again.

Can you think of one that really tears you up?
Whether it be from a movie (like when
Wil Farrell is on imaginary fire in Talledega Nights), or from an act (like Louis CK talking about most anything), or a cartoon (like when
Bugs Bunny does the square dance with the Hillbillies), anything will do.
Please add a link if you can so we can all watch it. If you're not sure how to find it, give us some clues and maybe we can help find it.