When a cousin of DH's got married, his bride chose the song "Phantom of the Opera" to walk down the aisle! It was played by a string trio, so at least it wasn't immediately identifiable, but it felt a little weird. I mean, it's Phantom of the Opera! The songs are beautiful and awesome and I love them, but not as wedding music.
Of course, some people thought I had weird songs playing before the wedding actually started, as people were being seated. My grandmother had made a joking comment a few months prior to my wedding that she was surprised I wasn't trying to incorporate Singin' in the Rain or Seven Brides for Seven Brothers in my wedding (those being two of my favorite movies of all time, and being love stories). I found copies of piano sheet music for some of the songs from those movies and asked our pianist to play them as people were being seated. My grandmother tells me she almost fell off her pew from laughing upon hearing "Singin' in the Rain" and "Bless Yore Beautiful Hide" as people were coming in!