Bugs Bunny is the all time champ no questions asked--the ones with the opera singer, the wrestler, elmer fudd, marvin martian ("the aludium Q-36 explosive space modulator!") etc will never be topped. I could go on and on. My alltime fave is "Duck Amuck" with Daffy at the mercy of an unseen animator that turns out to be Bugs. Absulutely hysterical.
My second fave would be the Flintstones especially the one where Fred inherited the mansion with the homicidal servants from his Uncle Giggles. Honourable mentions to the episodes with the way-outs, the Russian spy chick, the Beau Brummelstones, Ann Marg-rock, Stoney Curtis, and Boulder the detective ("when you lie on your back and cry on your pillow, tears get in your ears. Boulder's Rule."