Two things bother me far more than they ought to!
1) People who say anythink, instead of "anything" (let alone "anyfink!). I come across this all the time, partly because of the dialect around these parts. Turns out the word anythink has been around for some time (since the 1700's) but when I hear it used I know the people mean "anything", they're just getting it wrong. Happens with "somethink" and "Sumfin".
2) In written language, it's the misspelling of "lose", which is written as "loose", no doubt due to predictive text and the inability of a spell checker to notice.
Now, I have an accent, and being from Essex it's a weird one that commonly drops H's. I try really hard not to do that, but if I'm tired I can hear it coming back into my voice. Old habits.... And goodness knows, typing on the net isn't an English class, and I no doubt make more mistakes than most. Still, these two things bother me more than they should (online communication is primarily about being understood, after all).