In no particular order:
Futurama
The Addams Family
Corner Gas
3rd Rock from the Sun
Married... with Children
Honorable mentions (because I had a hard time deciding):
Fawlty Towers
Blackadder
Monty Python's Flying Circus (not technically a sitcom)
2 Broke Girls
Seinfeld
'Allo 'Allo!
Friends...