1. Office Space...Not really a true comedy, but I just worship this film!
2. Napolean Dynamite...I caught you a delicious bass
3. Fear and Lothing in Las Vegas...This is bat country!
4. Badder Santa *IM ON MY F****** LUNCH BREAK!*
5. Animal House...nothing beats it *was it over when the germans bombed pearl harbor?!*

1 dumb and dumber
2 happy gilmore
3 billy madison
4 caddy shack
5 napolean dynamite

all funny arse movies

in no particular order:

dumb and dumber
mallrats
bill and ted
snatch (not a comedy but funny bits)
old school

No geniune order:

-- Annie Hall
-- Harvey
-- The Graduate
-- Dr. Strangelove Or: How I Learned To Stop Worrying And Love The Bomb
-- Old School

Dr Strangelove
Natural Born Killers/American Psycho (satire comedy)
Clerks
Fear and Loathing
Schindlers List (:P)

I really can't think of a fifth.