Nine Inch Nails. Saw over spring break 2005 in Davis, CA. It was a show with only 2000 or so tickets. Truly awesome. I'd love to see him/them again.
Bob Dylan. Saw Summer 2004 in Boise, ID. It was 108° that day, but it was worth it. Mostly because I was smart enough to buy only one $4 bottle of water and refill it from a fountain.
Adema. October 2003. A really, really good show.
Crosby, Stills, and Nash. April 2003. I hope I can still carry a tune when I'm their age.
Everclear. Saw at some point in high school in Boise. This was my first concert. Marcy Playground and Fastball opened. Marcy Playground was far better the than other two. I wish they were still around.
Tracy Lawrence. So begins the country concerts list. This was actually a great show.
I think I've also seen (at some point) Johnny Paycheck, Confederate Railroad, and some other random country artists I can't think of off the top of my head.