I don’t have a lot of nicknames, I guess in part the fact that my name is resonably uncommon, people tend not to need to change it to identify me from others. :-)
Pretty much the only nickname I have outside of pillow talk is “dodocaptain” or some derivative shortened form such as “dodo”.
This cames back from my childhood – story goes that my younger brother couldn’t pronounce “Jethro” at the time and ended up saying “dodo”.
Since I was as egotistical back then as I am now, that ended up becoming “captain dodo” since I always wanted to be in charge.
In later years, when I first started using the internet (Win98 and a ZFree dialup connection, ah, takes me back ;-) I registered my first email address on Hotmail. Since captaindodo was taken, I became dodocaptain. :-)
I tend not to use it so much online these days (I use my realname for most sites) but bring it out sometimes for gaming.