The best fucking concert you've been to!!!

AFI in '99 about 10 mintues before they turned totally gay. that show was fuckin insane.

shadows fall/nevermore/inflames in '00 wouldve probably been my favorite but anders from in flames had the flu or some shit so they only played for like 45 minutes or something instead of a full set...but i guess perhaps the best would be:

KMFDM in '02. their first tour as KMFDM since like '98. awesome fuckin setlist. they didnt play all my favorites, but with about 10 albums of material to pull from they did a good enough job. awesome light show as well. only thing that wouldve made it better is if Skold was there, but he kinda quit to join/produce marilyn manson ($$$) instead. fucker. KMFDM in '03 was the shit too.
 
Agalloch/ November's Doom/ The Gathering

I've never been to a concert close to its perfection, the closet was Melechesh at Northern Lights 2004.
 
I don't think I can name one concert as the best ever, but I've seen some great ones. Some of the best are:

Metallica/Ozzy--1987
Megadeth/Slayer/Anthrax/Alice in Chains--Clash of the Titans 1991
Jane's Addiction--1991
Lollapalooza 92--Can't beat Pearl Jam, Soundgarden, Ministry, Ice Cube, Red Hot Chili Peppers
Nine Inch Nails--1994
Smashing Pumpkins--1993--This show was great, it was the week Siamese Dream came out, and so the band were still pretty small. It was a club show, great set. Talked to B. Corgan after the show. Before he was a whiny bitch.
Faith No More--1995
Tool--2002
Pearl Jam--2003. One of the best live acts out there

I've missed some great ones too:
I had tickets to see Pearl Jam play at a club right after Ten came out. I was in college and slacked on school stuff and ended up being too busy to drive out of town for the show.By that time the album had taken off and my buddies scalped my ticket for one hell of a profit and bought a bigass bong.
Jane's Addiction played at that same club in 1989. I was out of town w/ my family for Christmas and missed it.
Killing Joke played at a bar in 1989. I wasn't old enough to get into the show.
 
Maybe Metallica in '92 if pure intensity is what counts. Every Immortal concert I've ever been to was pretty damn great also. Some of the Mayhem/Burzum shows in the early nineties were also pretty sweet, although I suspect that I would be able to enjoy it more if it happened today.
 
- Megadeth @ Kerrang's 10th year anniversary, with newbies Friedman and Menza in the ranks

- Metallica @ Milton Keynes (with Megadeth, The Almighty, and Diamond Head)

- Clash of the Titans (Slayer, Megadeth, Testament, Suicidal Tendencies)

- Metal Gods (Halford, Testament, Amon Amarth, Immortal) - more for the fun than the concert, although Testament stole the show...this was the one where Abbath Doom Occulta himself told Gugs to sober up before the interview, just after Gugs nearly got into a fight with a bunch of 4ft Mexicans in the mosh pit, and the tour being cancelled that night because some fucker ripped off the road crew or something....

- Queensryche - Building Empires at Hammersmith Odeon (when they did Mindcrime in its entirety at their PEAK)

- Iron Maiden - Brave New World tour - it was cool to have Bruce and Adrian back on stage, and I was about 5 rows from the front-center at Madison Sq. Gardens

Hammers of Misfortune - last year....jesus, this band is godly

Agalloch - Cambridge, MA....muhammad, this band is allahy
 
I've seen a couple of good lineups in the early 90's..
Overkill, Pantera and Dark Angel
Laaz Rocket, Devastation and DBC
Death Angel, Forbidden
Kreator, Morgoth, Biohazard I think...?
Nalpalm Death, Sepultura, Death, hell I've seen so many shows many of them so long ago hard to remember the touring pairs..
Clash of the Titans was really good as well, Slayer, Megadeth, Anthrax, etc all on the same tour was kewl