I have a professional gmail and a "friends & spam" gmail and keep the two separate or "compartmentalized." Have to - -my professional address is often sitting open on my desk at work, and I can't have my father-in-law emailing me the latest picset of walmart ho's over the network there. Plus there are times I have literally dozens of emails coming in over that and I can't afford to lose track of them.
I have had a couple of forum names over the years too, but they are largely due to the changes in email addresses over the years--whatever email address I am using tends to be what I pick as a username. As far as online games, I usually pick some random nonsense word if Kyuss is already taken; if it isn't then I have the satisfaction of knowing that all the twats that try after it will get the "username already taken" that I usually get.
Now my wife has an interesting take on the significance of gender on online games. She will deliberately develop a female character and identity and use it to get free stuff from guys trying to impress her, in much the same way that guys buy girls drinks at the bar. I've watched her get awesome sets of free weapons, health potions, gold, whatever is of value in the particular game. She's also one of the best gamers I've ever met, so she generally ends up kicking everyone's ass then getting invited into the most dominant clan, team or whatever the case may be. Though lately she's been playing
Angry Birds, and the pigs don't really care that she's a girl.