Weird thing is my nickname sort of came from a game. My full name's Zachary, so I'd been going by "Zach" for as long as I could remember. When I was 14 I bought Stuntman for the PS2 (trial-and-error was pretty arduous, but it's a hell of a game). When I had to choose the name for my save slot, I tried to enter "Zach" but the interface was sort of confusing, so I accidentally cut off the end of my name and got "Zac". Then I realized that it was actually pretty cool so I stayed with it.
I don't have any other nickname more than one person calls me, except for my Chinese name, 何建宏 (He Jianhong), which must count for something because everyone here calls me by it.