I think I'm going to drop my vote for Monk and add a vote to something new to the list: Arrow Demon

Something is really wrong with this, especially for a CR 7. First off, it's mainly ranged, but it's CON is through the roof, giving it gobs more health than it should have (135 avg, compared to 33 for a Succubus of the same CR, or 135 for a Retriever of CR 11). It also has the ability to Dimension Door at will, which makes it almost impossible to melee, insane skills, and rather high saves for something of CR 7.

I think there were a couple other things about it that were broken, but it's late and I can't think straight…