Our gamertag is actually a combination of everyone's name in the family. We tried like 50 different names and they were all taken so that was kind of our last ditch effort and it worked.
lol...Mine's part of my name and a few numbers afterward. I did pay to change it to my married name once I switched all of my stuff over. The random numbers at the end make sure that my nickname is pretty much always available, whether for my gamertag, e-mail, etc.
My gamertag ended up being something completely random because every combination that I tried had been taken by someone else. I think it took me like an hour to come up with something!
It is pretty tough coming up with a gamertag, these days. Literally, just about everything you could ever think of is already in use. My gamertag was completely random, and I just got lucky that no one else had used it previously.
Mine is a combination of my favorite sports team and my birthday. I got lucky and the particular combination wasn't taken. I know people that have tried to create gamer tags for hours because everything they wanted was taken. That would blow.
My gamertag is something I actually had way before this generation started. The same name I use for PSN or Xbox Live is the same one I've been using since the earlier days of PC gaming