This is really hard, because I've been to some seriously great shows and events. In terms of Impact, I'd have to say Big Apple to the Big Easy. There were many reasons for this, but the foremost was Tom Waits.
I am an enormous Waits fan, and this was likely the only time I will see him in concert (though I continue to hope not). I went with murnkay, who actually secured the tickets after I bought seats to the wrong god damned day!
Waits played an unbelievable set. As a bonus, I ran into Stewart D’Arrietta, who was in town with his act, and was _also_ seeing Waits for the first time live.