The hardest I ever laughed was ...

Yes. Watch this any chance I get.

 

The hardest I can recall laughing, off the top of my head at least, was the first time I listened to Mitch Hedberg's two CDs while driving around town for work.
Some seriously incredible stuff there that would bring tears to my eyes, for the silliness of the joke sure but more for the incredible delivery of the material.
Some of my favorites:

"Last week I helped my friend stay put. It's a lot easier'n helpin' 'em move. I just went over to his house and made sure that he did not start to load shit into a truck."

"When you buy a box of Ritz crackers, on the back of the box, they have all these suggestions as to what to put on top of the Ritz. "Try it with turkey and cheese. Try it with peanut butter." But I like crackers man, that's why I bought it, 'cause I like crackers! I don't see a suggestion to put a Ritz on top of a Ritz. I didn't buy them because they're little edible plates! You've got no faith in the product itself."

"I was walking down the street with my friend and he said, "I hear music", as if there is any other way you can take it in. You're not special, that's how I receive it too. I tried to taste it but it did not work."

"I think Bigfoot is blurry, that's the problem. It's not the photographer's fault. Bigfoot is blurry, and that's extra scary to me. There's a large, out-of-focus monster roaming the countryside. Run, he's fuzzy, get out of here."

"My lucky number is four billion. That doesn't come in real handy when you're gambling. "Come on four billion!... Fuck! Seven. Not even close. I need some more dice."

"Sometimes I wave to people I don't know. It's very dangerous to wave to someone you don't know because, what if they don't have a hand? They'll think you're cocky. "Look what I got motherfucker! This thing is useful. I'm gonna go pick something up!"

Seriously. I could go on all day.

 

Maybe I'm just old, but none of these made me break a smile. I would have to reach back a while on these and give another vote for Airplane, Kentucky Fried Movie, Life of Brian, Robin Williams (I remember a bit opening SNL that went on way longer than I've ever seen there intro go, or once when he was doing Comic Relief), the first time I heard Steven Wright.

 

When I was in college, the student association would have various cheap movie nights for $1, showing films a few months after they left the theaters. The crowd was usually pretty raucous.

One night, they showed Cape Fear. There's the scene where Max Cady fights off three guys in the alley, then the Nick Nolte character, who is hiding behind a dumpster, trips over some trash.

In our audience, one guy did a perfectly timed "meow" of a cat. The place cracked up.

A couple other movie scenes:

Airplane: When the shit hits the fan

A League of Their Own: When Tom Hanks asks the ump if anyone ever told him he looked like a penis with a bow tie.

 

I LOLed out loud at this tonight.

 

Oh, let's see:

The first time I saw Animal House at the theater.

The "intermission" in Monty Python and the Holy Grail, when a couple of people in the theater actually got up and started to walk out.

The first time I listened the Richard Pryor's "That N-----'s Crazy" album.

Blazing Saddles at the theater, from start to finish.

Airplane!, especially the "I speak jive" scene.

 

When I was 21 and read the Chuck Norris jokes for the first time.

 

In an early episode of Family Guy, a reference is made to "when god told Abraham to kill Isaac" followed by a cutaway of Abe Lincoln shooting the bartender from Love Boat.

 

I was actually just thinking about this the other day -- how I had some of the most intense laughter experiences of my life with my best friend in middle/high school. I think I almost passed out at some point during each of these:

Reading an "elephant jokes" book
Watching "Ace Ventura: Pet Detective" for the first time. (Started at the beginning, when he's delivering the package, and never really stopped.)
Watching Eddie Murphy's "Delirious" for the first time

Some others:
Howard Stern's appearance on "The Magic Hour." https://www.youtube.com/watch?v=mF2soXgtxto -- There really aren't words for that if you've never seen it.
The "International Signs" sketch on The State: http://vimeo.com/7093133 -- caused me to fall off of my bed
And, probably my single favorite moment of comedic acting ever, courtesy Bradley Whitford: https://www.youtube.com/watch?v=zbx5SbJqsSc

 

I'll second the snowball fight from Dumb and Dumber. I thought I was going to pass out.

 

Borat. Not during the movie, although I laughed a lot then, but at dinner after the movie when we repeated our favorite parts.