Can't post the whole thing (too long and NSFW) but I've always marveled at the Nadia webcam sequence in American Pie. Masterful filmmaking and hilarious. Also have to shout-out the GOAT comedic actors Peter Sellers (pretending to be the German school psychologist Dr. Zempf in Lolita, the end hand scene in Dr. Strangelove, the fights with Cato in the Pink Panther films), Rowan Atkinson (pretty much every second of him as Mr. Bean is genius), and Jim Carrey (the mental patient football player in Ace Ventura: Pet Detective, the rhino scene and the tribal battle in Ace Ventura: When Nature Calls, the basketball game in The Cable Guy).
For an underrated pick, though, I love the first three minutes after the opening credits in Kevin Smith's Zack and Miri Make a Porno. I literally show this scene to students to break down the writing, the pacing, the editing -- another phenomenal piece of filmmaking and also, of course, hilarious.
