The Pink Floyd show was pretty loud. :p
Metallica was there in Summer 2003. That was pretty loud.
Not in Ohio Stadium, of course, but when Treg Lee made the basket with about 2 seconds left in the second overtime to go up 97-95 over Indiana, February 17, 1991, that was pretty loud. The fact that it was in an enclosed building helped to make it loud.
I wasn't there in 2002 when Allen intercepted the pass on the last play against Michigan. I'm sure that was pretty loud.
The Gamble interception was pretty loud.
When Herbstreit completed the pass to tie Michigan 13-13 in 1992, that was pretty loud.
Gonzalez's touchdown reception was pretty loud last year against Michigan.
When Ginn got out in the open last year during that punt return, it got pretty loud. But then when he passed the punter (did anyone actually think the punter would get Ginn) it got much louder.
Maybe the loudest moment I remember was Youboty's interception against Michigan.