My favorite, I think, is the instrumental theme to "Barney Miller". The earlier of the two versions, the one with the really good melodic guitar solo. In the later seasons, they redid the theme with a rather half-hearted guitar solo that sounds like random noodling more than a melody. But the original one was pretty great.

Edit: It's been so long since I've seen an episode of Barney Miller, I might just be getting it backwards. I just know there were two slightly different versions, and I liked one better than the other.