La Bamba. I made the terrible mistake of learning to sing it in 1990, then had to sing it between six and three nights a week for over twenty years. By now I must have played/sung it at the very least a thousand times and possibly close to two thousand times. I did it last night, and I'll do it again tonight. Close seconds would be Brick House and Mustang Sally, which I also sing, but not often lately. Those three songs always pack the dance floor, so I keep doing them. La Bamba was written in 1683, so it's the oldest song I've ever done also.
Maybe when I die my epitaph should read: He had to sing La Bamba over two thousand times.