Metallica w/ Queensryche opening at Capital Center in DC. Justice for All tour 1988 (when Metallica still had a primary hardcore cult following).
Metallica / G-n-R / Faith No More at RFK stadium summer 1992...it was the opening show of that summer tour so it kick major butt (well Metallica and FNM did anyway GNR sucked majorly live even though I like their music and albums)!!!
Rage Against the Machine at Michael's 5th Ave. Baltimore 1993. Most brutal mosh pit I've ever been in...which basically was 100% of the packed crowd except for the back 20 feet or so where they sold merchandise.
Suicidal Tendencies / Wrathchild America at York Fairgrounds PA 1989. Great show...Suicidal rules and is one of the most underrated bands of all-time!!!
Lollapaloza 1992 (I think) in Northern Virginia somewhere (Laurel Lakes???). Pearl Jam, Soundgarden, Ministry and Red Hot Chili Peppers. Best line-up of all Lallapalloza's in my book.
Pantera / White Zombie 1996 at Nissan Pavillion. Great show...Rob Zombie is an incredible entertainer!!!!
Oh, I've got to add Jimmy Buffet 1993 "Labor Day Weekend show" up in Boston MA. Probably the most fun time I ever had at a concert. I went with 30 college friends and we rented a Ryder rental truck for $40 a day and packed everyone in the back with a keg of beer. Completely illegal on pretty much all counts but at least only 1 of us had to drive!