Definitely David's added guitar solo in Dogs after the third verse. The definition of hardcore.
Another one would have to be the guitar and keyboard solos from Keep Talking, but only for Nick's drumming. I would put it up there with his best. My friend described it best when we were listening to it one time. "He's just having fun."
1. The Bass Fill in the silent part at the middle of On The Turning Away
2. The Choir singing the last chorus of On The Turning Away (DSOT)
3. 7:23-7:37 Comfortably Numb Live DSOT Peak Moment of the solo. Makes me Shiver every time.