Very many, and all of them acquired some time IRL:
"Maurice II" : Glassblowing Seminar - My appearance and personality reminded some of the older members of another guy they knew named Maurice, so they dubbed me his successor. These kids would later also run the debate club at my school and it became my debate name and default name to everyone else who knew me.
"Megadeth" : Track and Field - I used to make a lot of jokes about emos and metal heads during off-time, so they just began to call me "megadeth" - when I asked about it they said it was based on an old inside joke between some of the older members who said it was based on another conversation about what "The most awesome and extreme band name in existence sounded like", which was "MEGAAADEEEETTHH!!!" Yeah - they weren't sure either, but it stuck.
"X-Factor" - Also track and field - Nobody could remember my name, and the coach made it a priority to do so, so a lot of people just defaulted to calling me "X-factor". Still better than another one of the newbies who got called "Cocks" and whose brother was called "Lubes". In retrospect, i was quite lucky with my aliases from that time.
"The Ghost", or "The Ghost Kid" : Misc. - Room mates and fellow renters usually never see me or hear me make any noise when I move around so they used to joke about me being some kind of ghost or phantom - not an official nickname, but almost everyone I've come to live with has at some point made a comment or pointed it out.
"Captain Farley", or just plain "Farley": Sailing classes - I used to make wisecracks that reminded the instructors of Chris Farley. Soon enough, it replaced my actual name.
"Sargent Asshole", or "Sarge": It came from a club that took to bestowing code names to each other in the order of a military rank followed by a swear or obscenity (ex.: General Fucktard, Captain Shit, Lieutenant Damn-it). We all thought it was hysterical at the time.
"That Guy": Again, because nobody could remember my name. Eventually they came to know it, but they found it funny how they could not for a very long time and referred to me as "the guy", "that kid", and etc.; all in good fun.
TBH, I think it's because nobody really bothered to remember my actual name and didn't want to admit it, so they just went by whatever title I had at the time. Some of these are labels I pick up regardless of where I am repeatedly throughout time by different people.
*EDIT: Should probably add some context just as to how they were attained.