Alliance
The first nickname that stuck. It came into being when I was playing Dofus about 4 years ago, and I wanted to be a baker on my main character. I clicked the wrong thing, and accidentally started a quest which prevented me from becoming one until I killed a computer who was the sram class. I made a new character named SramSlayer. With that I beat the sram just to see if I could. After a while of playing as that character, I realized naming myself "SramSlayer" was bound to piss some diehard sram fans off. So I made a new character and named him "thesramtoenualliance." (Because I'm just so goddamn creative when it comes to names) People called me Alliance for short, and it just stuck.
Ecnailla
Alliance backwards for when Alliance was taken on games.
PhailMan
I really don't remember how this one started up, but I didn't get it from Dofus. If I recall it was a person called me PhailMan because I did something, so I renamed myself that and gave myself an avatar who I called PhailMan. (A red square with a yellow cape and a P on his side.)
(Heal)Mack
Another Dofus nickname. I clicked random and got Healmack. The name Mack stuck, but in general I choose either heal-mack or sober-mack. Most people from back when my heroic character wasn't dead remember by one of those 2 names. (This name caused confusion at times at times. I played Dofus with a guy named spizymack.)
Mateo
I got the nickname Mateo because my friend kept getting me and this kid named Mekkel mixed up. We call Mekkel a mexican, so then they started calling me Mateo. That's why I'm named Mateo on the forums.
To me, I find it more surprising that all of these names are names that I'm known by on the intrawebs than the fact that I use all of these names.