My older brother and I don't see eye to eye on many issues, but one thing which we are in complete agreement on is the most annoying thing one's roommate can do. That being, of course, not clearing the dishes from the rack, and instead putting the newly washed wet dishes over the dry ones.
Or at least, I used to think that was the worst. But this roommate, the fountain of annoyance that he is, has reached new lows. Oh, he does the wet over dry thing, but our dish rack is pretty small and soon enough gets so full you can't safely put another layer of dishes on. So he puts the wet dishes DIRECTLY IN THE CUPBOARD! He doesn't even wipe them or anything, just puts them in, as they are, dripping wet. And all I can think to say is WERE YOU RAISED IN A F***ING BARN?! Who does that?