Not just the theme, but Henry Mancini's whole soundtrack to Peter Gunn sort of redefined what series music could be: memorable, evocative, subtle, powerful, cool, hip, fully orchestrated.
I'm also partial to some other (really) old ones: Bonanza (it cries out "big, American cattle! and mountains and shit!"); The Jeffersons ("Well, we're movin' on up!").
Mike Post -- king of washed-out, meaningless, inoffensive drivel. Ever see him and Bob Crewe in the same room together? I didn't think so.