So, I guess I'm on a music theme here, but it seems I've been talking to a lot of couples about music lately. When the subject of processional and recessional songs comes up, I always advise them to just play what they like. The only caveat is that you should be sure to listen to the lyrics and make sure they won't be embarrassing on your wedding day. In other words, do you really want to realize (too late!) that you're walking out of your ceremony to a break-up song?
Many people already have plans for playing non-traditional tunes. One of my all-time favorites was this "classical" version of Guns 'n' Roses' "Sweet Child O' Mine" by Vitamin String Quartet. It was chosen for the bride's processional and it was great! Guests who recognized the song loved it, and the others just thought it was a nice, energetic classical piece. Brilliant!