Of course Judah/Tszyu. Berbick and Tyson was the second one I thought of when I read the title of the thread, with Berbick flopping around like a landed fish, which somebody already mentioned. Foreman was pretty wobbly and staggering around when he went down against Ali.
It is old. But for the record, my favorite was when Miguel Cotto was BADLY staggered by Demarcus "Chop Chop" Corley in '05.