I walked down the isle to Ave Maria, it's a beautiful piece of music and lots of different versions to choose from. Are you getting married in a church?
I think it's best to pick something that embodies the spirit of your wedding. For many that means the traditional wedding march.
For us (this July), we're getting married on field with a marquee for the reception, bales of hay to sit on outside and home brewed cider to enjoy in the sunshine. We're going with All I Want Is You by Barry Louis Polisar as it's really fits with the country feel of our big day