The closest thing to a "dud" that I can think of would have to be Iron Wolf at SFGAm. The thing is, I really like the layout, unlike most B&M's the layout is not predictable, and it does not include any massive elements. Rather, the ride is very tight and compact with lots of sudden changes in directions. The problem is, its a stand-up, and those changes in direction do not bode well for your head. It is probably about the only ride that makes me angry when I ride it. Everytime I go to SFGAm with someone, they always want to ride IW, even though I tell them they shouldn't. It has never failed that everytime they get off the ride they tell me that I was right, though unfortunately I usually end up going on it with them. So i guess u could call IW a good concept, just bad execution. Maybe you could call it a half-dud, cause without the headbanging, I would really love the ride.