Mine is NULL. Null means invalid, non-existent, void or in this case, incomputable. Essentially it expresses I'm a total nut when I play and thus unpredictable/chaotic. Nothing too complex or special, literally just a description of how I play.
I rep the service tag "WOLF" just because I feel like it matches my playstyle; I can hunt in packs, but I can survive on my own. I also rock the "Lone Wolf" emblem, really hoping they bring it back in Halo: Infinite.