Originally Ree-c, then Naga-c, now just Naga in the rare occurence that I open SRB2. I use purple (HOT PINK), just because I can. :3
I use the same names, regardless of the game. Alternative nicks include "Mario" (Halo, my friend Chris/Cross used Luigi), and I tend to use the default name "Nomad" in Crysis whenever I haven't played for a while, so I can get used to the game again without worrying about people thinking "Naga is bad at this". Though, I do this in what may also be a laggy game, but I tend to rename myself afterwards.