I was the only kilted guest at a wedding a few years ago, but it was at the specific request of bride and groom. Most of their friends thought it was cool, but the older generation was somewhat more dubious. (The groom's grandfather was from Edinburgh, and I couldn't quite tell what he really thought.)

The flip side is that I've been invited to another wedding this fall, which will be a "black-tie" event. The bride (big LARP/ren-faire fan) has always been keen on kilts, and I figured it would be a no-brainer to come in my PC get-up, but asked anyways. I'm very glad I did as she actually said it would be better if I came in a traditional tux or suit, due to the conservative tastes of the other guests. A bummer, but it's her day. Now I just need to find new trousers that will fit a tux that I bought back in high school!