I've had 4 nicknames since high school.
Rats
Uncle Kevin
Kepo/Kepy
Judas
Rats I got because my baseball coach in high school couldn't say my last name right, its pronounced "Reh-Tee", but he kept calling me rat-tee. So everyone started calling me rats.
Then after high school, when I was about 19, i looked probably almost 30, and all my friends looked young. So because I looked so much older, they started calling me Uncle Kevin, which I always hated that nickname.
And since I hated Uncle Kev, they morphed that into either Kepo/Kepy for some weird reason. Thats mostly what everyone calls me now.
Judas came about because it was a friend of a friends birthday, and we went out to the bar, and at this bar I saw a girl I used to know, and I basicly ditched my friends to go make out with that girl instead of hanging with the boys. They said I "Judased" them. Then they started calling me Judas as a joke, and it kind of stucked.