Oh man this could be a good thread as there are so many possibilities. If you are going with Seinfeld "The Contest" has to be in the conversation as one of the funniest episodes of the series.
[video=youtube;61zJHstzOoY]https://www.youtube.com/watch?v=61zJHstzOoY[/video]
A funny exchange within that scene, one I had forgotten:
Elaine: My friend Joyce is teaching an aerobics class, I’m gonna go tonight.
Jerry: Yeah, the waitress should’ve taken it back.