When I saw Anthrax in the early 90's the pits were pretty intense, but also, the venues were sold out and jam packed and just generally crazy. The best pits I've seen since then have been at the World Series if Metal 1996 because there was no barricade and stage diving was allowed, and later on in 1998 they played a small club on the outskirts of Cincy on a night of from the Pantera tour. It was early 1998 in the midst of week of snow and shitty weather. Anthrax weren't yet promoting Vol. 8, they were just jamming and wanted to headline after opening for Pantera since November. Alot of old school metal heads packed the place, got boozed up and went ape for Anthrax.
THe best pits in the business are Slayer hands down. You can't escape the wrath of a Slayer pit at all. It's like the Hotel California, you can check out any time you like but you can never really leave. You go to the balcony of the venue, there people beating one another up there. You go to the restroom, you're liable to wind up face first in a pile of piss, you go to the beer line, good luck holding you beer up. Slayer pits rule. A close second goes to Pantera, because they always play arenas, and if you climb out of the pit and go up high, you can almost always count at least 4 good circle pits on the floor!!!