I'm not talking commentaries that are mildly amusing or full of light chuckles. I'm talking about commentaries that give you a good number of big laughs.

Here are a couple for for me:

Clerks Director's Cut 10th Anniversary DVD
One Crazy Summer

This is Spinal Tap's in-character commentary

Pretty much any Kevin Smith commentary. The in-character Spinal Tap commentary is probably my most-listened to.

Dogma. Kevin Smith rocks.

One unknown (But hilarious) commentary I've never forgotten is for Skin Deep (2003). Co-star Steve White's humor starts from the opening scene and never lets up.

Road House. Never enjoyed the film as much.

Arrmageddon, Afflecks portion. He spends most of the movie ripping it. Best part was Sling Armageddon

Goonies.

The group commentary on the Japanese martial arts/samurai/zombie flick Versus. A total hoot, they must have had a blast doing it. Have some fun! Ah-so!

Cannibal! The Musical - A drunken commentary where the cast starts out playing a drinking game with no clear rules. 10 minutes later: "Is the Scotch already half gone?" At about an hour in: "You know what, fuck Sting!" End of the movie: "Let's go to a titty bar!"

I'm a big fan of:
Joe Bob Briggs Commentaries in general (especially Samurai Cop)
Rock N Roll Nightmare
Black Roses
Vice Acamedy Series

John Waters does great commentaries.

I know I've asked this before, but I can't remember the answer, but has he done other commentaries (yes, I know his 'I Spit on Your Grave' commentary is also hysterical).

Yes, these are the others, and my ratings of their hilariousness (out of 4 stars):

Warlock Moon: 2
Blood Sisters: 2
Double D Avenger: 2
The Hollywood Strangler Meets the Skid Row Slasher: 3
Run Angel Run: 3
Hell's Angels 69: 3
Jesse James Meets Frankenstein's Daughter: 3
The Incredibly Strange Creatures that Stopped Living and Became Mixed Up Zombies: 4
The Chooper / Blood Shack: 4

Samurai Cop and I Spit would also be 4 stars.

Oh, and I'd add Used Cars to the list of funniest commentaries:

That's nothing, you should of seen what kind of trouble my neighbor Jeff Dahmer used to get into late at night back in Milwaukee. A kinda weird dude, but always ready to lend a hand or foot when you needed one.

Used Cars is a great one.

I'm also a HUGE fan of the commentary (in character) on the Region 2 release of Gareth Merenghi's Darkplace

I found the Knocked Up commentary to be pretty funny, primarily due to Bill Hader doing impersonations of Al Pacino, Vincent Price, and others.

Some of the Futurama commentaries are tremendous. It's clear those writers and actors were having a wonderful time and their laughter can get pretty infectious.

"Nobody caaaaaares! Nobody caaaaaaaaares!"

Recently watched (heard?) the commentaries on 40-Year-Old Virgin and Knocked Up, and they were fun. Seth Rogen's laugh got to be a bit grating, but otherwise, they were good. Also enjoyed Danny Leiner, John Cho & Kal Penn commenting on Harold and Kumar Go to White Castle, especially when Penn gets caught up in discussing his love for Dude, Where's My Car?.

I actually sold my copy of Goonies due to the annoying Corey Feldman commentary... I have since repurchased (black friday sale) but I vow to *never* turn on that track again. ha ha ha

and...
Carrot Top on Rules of Attraction is one the funniest commentaries.

Kentucky Fried Movie

Used Cars is good and Bobcat kills on the One Crazy Summer commentary.

Anything with Garry Marshall. All the guy has to do is start talking and I crack up. Runaway Bride and Princess Diaries, the commentary is better than the movie.

Seriously cannot believe this thread has gotten this far without a single mention of Tropic Thunder. Downey in character talking about peeing had me laughing as much as the movie did.

Some others not mentioned; Spaced, Arrested Development, Mr. Show has some hilarious lines in the commentaries.

I have actually held off on this one for a particularly snowy day. You've made it harder for me to postpone it.