None other than the well-known ATH-M50. Here's why:
1. I find them far too uncomfortable.
I even ordered new pads because I thought that was the problem, but apparently not. I stretched them for days and it seems that nothing has helped. There's always an unpleasant pressure near the bottom of my jaw and the headband is terribly thin. This is the main reason I dislike them - I just can't enjoy my music without noticing how uncomfortable they are.
2. I don't think they're worth the $120 price tag.
Speaking from a consumer standpoint, they sound nice but reviews online build up the tension perfect for disappointment. To the untrained ear, the difference in sound quality is not proportionate to the difference in price. Alright, this may be a personal issue/preference, but it's still an issue in my book. This actually transitions into my next point...
3. They could sound better.
I do like the V-shaped sound signature, but I don't really like the soundstage. I like my soundstage either very close or very far. Also, I'm not a basshead but I think I would like a bit more bass impact (I have the white box version, which is apparently more neutral). I also find them a bit too harsh/sibilant/bright? I must have delicate ears. Otherwise, I think they sound quite nice across the board but for $120 I wish I got a bit more.
4. They're too bulky for my tastes (also see: not portable in the slightest).
I know, they're obviously not built to be portable cans...but why, then, do people still recommend them as such? Anyways, they're very bulky (although fairly light in comparison to the SRH440s) and the cord is absolutely impractical for pocket storage. The cord is not detachable and has no remote/mic option. It's also fairly incompatible with my computer, which has its headphone jack on the front, making the cable hang down on my lap as I browse...which is annoying. Wearing them around the neck isn't too comfortable. All in all - why anybody would take it outside is beyond me (although I've seen it happen before).
Conclusion: I just don't like 'em. Should've tried something else like the Shures (440s) or Ultrasones (580s/780s). Maybe the Senn HD558s, because I'm interested in the open-style sound.
