When my wife and I got married, we asked my daughter to be the maid of honor and my son to be best man. Son said he couldn't be best man, because the best man is a groom's attendant, and we didn't have a groom. We ended up compromising by calling him the dude of honor.
I have a man of honor! I am pretty reserved and don't have many friends, especially because I'm a workaholic teacher in a very rural area. But one of my fiance's close friends, a guy, has been so welcoming to me for the past 3 years and has really become a great friend of mine, and he agreed to be my man of honor.