As for sheer inspiration, Paul McCartney's bass on the Sgt. Pepper album. Also, Hey Bulldog, a song which Geoff Emerick said had the most inventive bass line since Pepper. It's really John's song, but I do like Paul's bass on it. Of course, trying to single out specific Beatles songs is not exactly something which can be done without some forethought, and I've never tried being a Beatles expert anyway.