Two movies I can see anytime they air: CADDYSHACK and BACK TO SCHOOL. BACK TO SCHOOL was so freakin funny. Rest in Peace, Mr. Dangerfield.
I also loved "Easy Money" - it wasn't as commercially successsful as the two you mentioned, but was it funny.
"Ohhh, I can't eat all my home fries - you want some home fries?"
Joe Pesci: "I can't explain it, I got no.... I got no...."
Rodney: "Class!"
He stole every scene of his in "Caddyshack," much to Ted Knight's dismay.
Remember that scene with Sam Kinnison?