I don't know if it's been mentioned, but...
DLR.
Why? You listen to a whole CD of him, and you're annoyed. Imagine having him in the band.
Look, I like hearing DLR in small quantities, but, too much DLR has to be unhealthy.
Scott Stapp - I dunno, the guy's voice just pisses me off.
Scott Wieland - zero vocal range, and, he sounds like the singer in my last band, which is even more "ammo"