Animal House, that takes me back to my teen years, loved Belushi.
Someone mentioned Young Frankenstein, that has to be one of my all time favs. Best scene for me was Peter Boyle (the creation) happening upon the blind guy (Gene Hackman) that was priceless.
I'll pop in two more film names - Arsenic and Old Lace (Cary Grant) and Harvey (James Stewart) both hilarious.