Something I can't help thinking and I don't know why, but it just really... bugs me. Why do some native English speakers substitute the letters "th" for "f" and even "v"? It makes me cringe when I hear it. Accents I get, and non-English speakers I get, but when someone just down my road, someone who's as English as Yorkshire pudding and Earl Grey says things like "I fought you were going to do that fing today. You know, that fing you said you were going to do? Did you fink I'd forgotten?" or "That leaver jacket looks like it came out of ve Matrix." It just makes me shiver inside and think "Why are you speaking like that?!"
Ugh, sorry. Just one of my bugbears I guess.