Talking with some of the guys at work about it tonight, and got some interesting answers. I'd have to rank my top 3:
3) Pantera - unGODly loud! Dime came out and ripped right into "Cat Scratch Fever" and you could literally feel Vinny's double bass hitting you in the chest.
2) George Thorogood - I went to the show just to see Marshall Tucker Band open, and left talking with my dad, and we both said it was one of the best shows we've ever seen. That guy puts on a show, and really interacts with the crowd. I'd drive 6 hours to see him again if I got the chance.
1) Skynyrd - I've seen them perform over a dozen times live, but one show really stood out to me. After Hughie Thomasson passed away they did a show 3 days later in NH, and I sat 3rd row. Ricky Medlocke played the entire Freebird solo by himself, and half way through I looked up and he had tears running down his face.