Many, but the ones I'd like to point out are the loving COX COMMERCIALS.
Sometimes it's the awful music that makes me gag, other times it's the bad acting and hideous actors.
Usually though, it's the fact that they blatantly defy the set volume level for the rest of the channel. I watch the history channel a lot, and they have the loving volume set somewhere around 5 less than the typical volume you'd hear on other channels. This makes me turn the volume up every time Deadliest Catch comes on and makes me leave the Discovery channel in disgust.
I'm watching at a comfortable volume, then a Cox commercial comes on wakes my parents up with the worst music you'll ever hear on TV.