I always liked this show called “Renegades” or something from a long time ago. I distinctly remember one guy dressed as a policeman, throwing his baton between someone’s ankles and causing them to trip and fall. This maneauver was practiced countless times by me in the early 80s always to no avail.
Special Unit 2 (oh, it wasn’t great or anything, but it WAS fun).
I’ll second The Lone Gunmen.
Mystery Science Theater 3000. There were so many more bad movies to shread.
Max Headroom
And I’ll second Cupid.
Off Centre
The weird thing is it used to do horribly in the ratings–but the WB brought it back anyway.
Then they killed it after about two shows into its second season.
Police Squad! (in Color)
Adventures of Brisco County, Jr.
I wish The Lone Gunmen had more of an opportunity to find it’s “nitch”. I really wish the series was more like the two “Lone Gunmen” episodes on The X-Files. They weren’t as silly as the series. There was an episode in the series that spoofed The Green Mile, after an inmate got out of prison, he opened up a hospital for roaches, that’s just stupid.
Family Guy most.
Quantum Leap, The Pretender, Firefly as well.
WKRP in Cincinatti
The Misfits of Science
Emeril 
Barney Miller
Millenium, I wish they’d pulled the plug on entirely after second season if the only other option was the third one it did have. It was curious–it had characters of the same name being played by the same actors, but yet…ah well.
American Gothic I’m still bitter about, but I suspect that it wouldn’t hold up to my memories of it.
Kolshak, the Night Stalker, should never have been cancelled.
MachineHead, my comment was a reference to the disappearance of Who Wants To Be A Millionaire?, the show that replaced Clerks.
-Now and Again
-Sports Night
-Cupid which has Jeremy Piven AND that rather attractive actress who I can never remember the name of, you can’t lose!)
-LA Doctors
-Dharma and Greg
-Traders
I know there’s more, it seems that there are three or four shows cancelled every year that I like…
The Tick.
Birds of Prey (OK, it sucked, but it didn’t get much time to find it’s way. Maybe if they’d fired the director, the producer and all the writers and started over … oh, maybe I don’t mind so much that it was cancelled…)
…and I will fourth the Lone Gunman. I miss those guys…
and I haven’t seen it when the X Files Jumps the Shark ( 
) but when I do, I fully intend to turn the TV off before the last five minutes…
I’ll chime in on Quantum Leap and The Pretender and Early Edition. Also Strange Luck and Nothing Sacred.
The original Star Trek