X-Istence came when I was moving away from an old nickname. At this time I was dubbed the destroyer at my high school, so existence made sense, except I just liked the idea of xistence without the extra E to make it more Internetey and then came off course X-Istence, where X was meant to stand for Extremely and the I for Insensitive, as I really at the time did not care about anyone or anything.
0x58 came along later when friends thought my nickname was too long. 0x58 is uppercase X in the ascii table. Later I have been known as x58 or just 58. 0x58 also came in handy for the hacker community as the lower the character count in the nickname, the cooler you are
After watching Idiocracy I was also dubbed BeefSupreme by my professor who is also a very good friend. Shortened to Beef over the phone and in person, so it tends to confuse people. "What's up beef?" *people look around the room in confusion* "Nothing, what's up LosT?".
Nyt_Muves from another forum, the brother of the professor nicknamed LosT, also tends to call me Untgrad (Idiocracy as well) since the main character in the movie asks:
"Upgraydd, that sounds Dutch, I once knew a Dutch guy, his name was Untgrad"
I go by many nicknames, and I don't mind. It is interesting to me, and keeps certain parts of my identify undisclosed with certain people, or lets me have two entirely different "faces" when talking to people.