I saw Static X open for Fear Factory and Disturbed in the basement of a church in Scranton, PA. This was back in like '98 range. It was a REALLY cool concert experience. The walls/floor of the basement were concrete. It was so fucking loud, but the entire area was a mosh pit. And if I remember, the stage was only about a foot or two in the air above the floor and the ceiling of the place was only 10 feet total. My favorite concert to date.
I wish I had gone to the Metallica Free Concert in Philly at the old Vet Stadium, but my boss (dad) insisted that I come in to work that day. I still regret not going to that show.