An episode I don't see frequently is the Pig-Man.
I just recently saw it for the first time in awhile. George: "He's not a pigman, is he?" Kramer:"No he's just a fat little mental patient."
The one I never see on reruns is the "Puerto Rican Day Parade." Not the funniest one, by a long shot, but it was the second-to-last episode and had some funny moments.