I think the only really viable options are song, artist, album, or video. As I stated earlier, I rarely watch music videos so I won't be voting for that one... I think Tim pretty much summed up the likely top 5 in his earlier post... The album list was interesting but albums seem to be less relevant these days...I say go for songs again.
I'm up for whatever Video would be nice, although I couldn't compile a list of more than 15 or 20 videos (not counting U2) from the top of my head Never been an avid videoclip consumer...