It's A Mad, Mad, Mad, Mad, World...I still laugh every time I watch
I always loved that movie. I watched it recently. There was basically a remake of that called Rat Race. Without a doubt, in my mind, the funniest movie ever. My favorite scene:
I remember being in the army watching Porky's with a bunch of paratroopers. Not sure if we were delirious but I have never laughed so hard as I did the first time I saw it. We were literally falling on the floor. So many funny scenes we went home with stomach aches.
Porky's: Principal's office
Other good choices, but I don't consider them hold you sides funny:
Something about Mary
Princess Bride
What's Up Doc
Arthur (the original)
Airplane
Caddyshack
Monty Python
Smokey and the Bandit
Blues Brothers
Cannonball Run
Television has so many - how could you even chose?:
I love Lucy (the standard bearer)
How I Met Your Mother
(You know, Barney, for anyone else, this would be a new low but sadly for you, it's just a new middle)
Seinfeld
Married With Children
South Park (if you get the right episode)
Always Sunny in Philly
Big Bang Theory
2 1/2 Men
The Office
Friends
Reno 911
Brooklyn 99
Will and Grace
30 Rock
Kind of Queens
Up Schitt's Creek
Becker
Spin City
F Troop
Gilligan
Cheers
Frasier
Taxi
WKRP
That 70's Show
The Cosby's
Home Improvement
Everyone Loves Ray
Either Bob Newhart
The Mentalist (definitely not a comedy but Patrick Jane makes you laugh)
and these are just off the top of my head..........