Eh, for me, it really depends on the name. Heck, I usually find names like "Xx-|Sefaroph|-xXLMFAO!!!!11eleven" the most offensive because that just means the person didn't take the time to come up with anything original... especially when they misspell the name "Sephiroth" either due to their own ignorance or because the game forced them to, and then "decorate" it with X's and other random punctuation...

Either that, or the horribly bad weeaboo Japanese names (although I admit "Tetsaru Arigashi" isn't much better, lol). But yeah, unless it's just outright racist or something, I usually find it humorous or entertaining to try to look for the craziest and most memorable character names/ID's I can find, and sometimes I even try to come up with some of my own, like "Geezer T. Dudeface," or possibly making a Lalafell mule character named "Tetstaru Lolifail."
Some I've seen from various games:
Baron von Rammerhimen
Bigassmanlydykes
Jesusofgod
Feck Me/Fook Me/Fook Yu
Moron
Hamburgermeat Heartthrob
Strumpet Unfufudu
Imagene Yuss
Me Sofa King We Todd Ed
Or people who make "clone" or RP joke characters and then run around acting just like them. I remember making a Bill Cosby character on PSU just to troll people with phrases like "Here I go! DOOWWWWN the slope...", and later on I found a Lord Ilpalazzo from Excel Saga running around saying "This world... IS CORRUPT!" Crazy stuff like that is hilarious to me.
I mean c'mon guys, who here hasn't played Pokemon and named their rival something like "Dumbass," or their Metapod or Kakuna "Penis" just so it'd say "Penis used Harden!" ? I know people do that stuff all the time on various games just for the lulz... myself included.
