The original version of Rat Race, starring everybody who was anybody in the comedic acting scene of 1963. I especially like the performances of Ethel Merman and Jonathan Winters--who respectively play an overbearing mother-in-law and a dimwitted trucker.
I also really like the scene where Terry-Thomas and Milton Berle engage in fisticuffs because, like their characters, I wouldn't have the faintest idea what to do in a fistfight.