(Somewhat archaic) chatspeak for "grin," deriving, AFAIK, from IRC.
See *g*, which is more common nowadays, especially on AIM.
A: So this cop pulls over Dr. Heisenberg and asks, "Do you know how fast you were going?" He replies, "No, officer, but I know where I am!"
2. A cool person that's "wit it"
3. someone close (either sex//male or female)
(NOTE*: All of the above is strictly for internet use)