"Old" is such a broad term. It could mean anything from Howdy Doody to Veronica Mars.
Ignoring the obvious hits from Gunsmoke to Mash, here are a few gems that I would consider less well known:
Captain Power and the Soldiers of the Future
Space Cases
Police Squad! - Everybody remembers the movies, the TV show doesn't get enough love)
The Munsters - Addams Family had better movies, but this was definitely the better of the two original shows. Also, shut up about Uma Thurman.
And here's a couple shows that aren't actually good, but if you're doing a history run you should have at least have an episode or two in your catalog:
Ghost Busters - No, not the Ghostbusters. The original TV show with a gorilla as a main character. Also, the reason why the cartoon had to be called "The Real Ghostbusters". It's really bad, but fun for an episode or two.
Supertrain - An amazingly notable sci-fi-ish failure. I can only imagine how much cocaine was involved.
My Mother the Car - You see a lot of parodies that make fun of this. Some people don't know it was a real show. And really stupid.
I have The Man From U.N.C.L.E on DVD as well as Star Trek: The Animated Series, WKRP in Cincinnati, The Muppet Show, and Jonny Quest.
The Real Adventures of Jonny Quest is the best version of Jonny Quest.