I'm not sure anyone has mispronounced my username, especially because of that tricky x (and that it's new).
It's toy-cks. Like Twix, but weirder.
However, on other games where my username is Kuro, some people mispronounce it all the time. I've heard koo-ruh, kuh-ro, and incorrect emphasis on the wrong syllable.
It's more like coo-ro, with the emphasis on the ro and a roll on the R. Needless to say, I just tell them to call me Toi. Kuro is weird to pronounce.