We all have our favorite lines, but what about the great silent bits in Seinfeld? There are lots - here are two of my favorites:
1) George and Jerry waiting while the tape rewinds in "The Soul Mate". Normally a sitcom will avoid "dead air" like this, which is what makes this scene so funny. They just stand there waiting, looking uncomfortable.
2) Newman with the dental tape in "The Sniffing Accountant". He tries it, says he doesn't like it, and places it oh so carefully on the dash of Jerry's car. The disgusted look on Jerry's face is hilarious.
Any others?