What movie makes you laugh every time you see it?

Tommy Boy, just about every scene I can think of.

I am disappointed so far by the answers. here are the real comedies:

Brain Candy (psychological mumbo jumbo)

Airplane (we're all counting on you, good luck)

Kentucky Fried Movie (enormous genitals!)

Amazon Women on the Moon (don simmons)

The 3 Amigos (do you have anything besides mexican food?)

The Naked Gun (dutch irish, my father was from wales)

The Naked Gun 2.5 (delightful)

Top Secret (only movie with scenes shot in reverse and an underwater bar fight)

Animal House (Double Secret Probation!!)

Run Ronnie Run (very underrrated)

Something About Mary

The scene where the PI is trying to revive the dog, the scene where the dog attacks Ted, the "hair-gel" scene, lots more.

Jay and Silent Bob movies

Saving Silverman

the movie zoolander. the whole movie is funny but these parts are my favorites:

what is this a center for ants???...it has to be at least..3times bigger than that!

god is that you?

merman father!!merman!

the awards ceremony, and the gasoline fight

im not an ambie-turner(dont know how to spell it)

well derek im sure there are a lot of people who cant turn left...

how did you know you wanted to be a model?

well one day i looked into my spoon and said wow your really good looking. maybe you could have a career in that.

in what?

in being professionally good looking

well pretty much the whole movie is funny.

Raising Arizona

Anchorman

The Royal Tenenbaums. Smart and Hilarious.

Zoolander

Rat Race always cracks me up. From start to finish it's so outlandish and crazy. I like the way it makes fun of reality TV shows (although I admit to watching them). Very funny movie!

The Princess Bride.

Particular Scene. In the Fireswamp when Westly says there are no ROUS and one jumps out and gets him.