The hardest I ever laughed was ...

Delirious
Bad Santa
The first time I heard Dice Clay do nursery rhymes
The Palestinian Chicken episode of Curb
The Funkhauser joke to Seinfeld on Curb
Springtime for Hitler

 

This photo got my coworker and I laughing so hard, our boss finally came out of his office and yelled at us to settle down.

 

Sermon on the Mount scene in The Life of Brian is probably the hardest I've ever laughed.

Every Sperm Is Sacred from The Meaning of Life is a close second.

"I call the big one Bitey" from The Simpsons' Marge vs. the Monorail is up there, as well.

 

Good call on this. I saw this in theaters and I laughed so hard I missed just about all of the dialogue for the next scene or two.

 

Debbie Downer's first appearance.


And, you have to hear Mitch Hedberg's delivery to get his humor. Reading it straight is good for a chuckle, but with his timing, it's hilarious.

 

Love the marine biologist one, especially at the end as George tells his story. If I recall, the dialogue was only written the night before filming.
"The sea was angry that day, my friends. Like an old man trying to send back soup in a deli."
https://www.youtube.com/watch?v=0u8KUgUqprw

Another of my absolute favorite episodes was "The Little Kicks," where Elaine "dances," Kramer's friend Brody the bootlegger has issues, George tries to be a bad boy and Jerry is a bootlegger. So many great scenes and lines from that episode. Sweet Fancy Moses!
https://www.youtube.com/watch?v=xQ39WeJpDLQ

 

Yup. Good call.

 

The turkey drop scene gets a lot of play, but the violins during the WKRP softball episode always kill me.

http://www.dailymotion.com/video/x9wlc3_baseball-2_auto

 

"Barney Miller" - The hash brownies. Fish leaping across rooftops chasing a suspect. Yemana getting all effusive about how they get "mooshie" in coffee. And:

Barney: Harris, take these and get them analyzed, fast. (Harris starts to eat another brownie.) NOT THAT WAY!

 

Several scenes from Woody Allen's "Bananas." The one where Allen helps a guy backing into a Manhattan parking space and after the guy rams the car behind him gives him the OK sign and walks on, finding supplies for the revolution by ordering deli takeout. "I'd like 750 tuna fish sandwiches, etc," and of course, the opening scene, Howard Cosell broadcasting an assassination for "Wide World of Sports."

 

"Dead honky!"