I'd have to say Seether. Of course when I went to the Greensboro, NC show, I was there for Staind, but I ended up fucking my voice up singing Seether, but my favorite time at a Staind concert is trying to finish Mudshovel without dying :D
Would have loved to see them with sevendust missed that tour. I hate seether again just my opinion. But I would have to say opening band would be papa roach.saliva, or cold. But I saw them open for godsmack and that was awesome.