I'll never forget the first band I was in and the other guitarist thought he had come up with an original riff that was simply the barre chords A, G and F (if I remember correctly, just three all one step apart). First he played them going down, then he reversed them and played them going up.
I could swear it was a Procol Harum song (in fact I thought it was Conquistador), but now I can't find it... Bah.