I used to use a nickname for online gaming. Recently, though, I dedcided that it was obnoxious and somewhat embarrasing to go to a LAN party where everybody calls each other strange nicknames. They don't sound nearly as cool when spoken out loud.
Especially when about 50% of them are some variation of "Death", "War", etc...
"Hey Deathstalker, is the router back up yet?"
"Sure thing, Deathmonger! Wanna fire up some C-Strike?"
"Awesome. Let's ask RedDeath, Daddydeath, and Bloodsucker if they want to join in."
"Great. I'll go find Wargamer and see if he'll host."
All of the above are real nicknames.