Inspired by the passing of James Garner, as The Rockford Files had a pretty cool theme tune composed by Mike Post (who also wrote the Hill Street Blues and A-Team themes, amongst others).
For me, it has be a tie between The Littlest Hobo & (despite it's rather dodgy lyrics) The Fall Guy. Oh, and the lovely sweeping orchestral piece that Granada used to play at closedown (remember those?!) in the 1980s.