Do you promote your forum through gaming multiplayer? How has that worked out for you? How do you promote? (Bio page, send messages etc...) does it bring traffic?
Long ago I use to make my Steam name my website domain name. Also, when I was playing online I would make my in-game name the URL of my website. People would ask questions over the mic and I would answer. got some traffic and new members. So, yes it does work as long as you use it properly and don't spam messages just play the games you love with the URL as your name :]
Although most fans of metal music tend to be gamers, we've never quite entertained the idea of advertising on gaming communities. It doesn't seem to help us too much.
I think it works but it depends on your niche. If you have a gaming forum, then I think this method will work better than if you have a promotion forum. The chances are there will be some webmasters that play games so you may be able to bring members to your promotion forum if lucky. I think if you don't spam messages and use a more natural method such as waiting for people to ask about it, then it could bring some members to your website.