Hagler-Obelijamas Rd 4 and on nothing but good action. If you haven't seen this fight you need to. Holyfield-Tyson 1 rd 11 deserves a shoutout.
Corrales-Castillo for me its like something out of a damn movie. Big left hook and down goes Corrales out comes the mouthpiece, hes up then another KD and other spit, the ref deducts a point for it and Gossen tells Corrales you really gotta ****ing get on him now. about 40 secounds later Corrales scores a KO with a limp Castillo getting battered on the ropes.
Thompson-Rothmann rd 9 just watch it [ame]http://www.youtube.com/watch?v=VUaVTXyjQbs&feature=related[/ame]
If I had to choose just one, it would be round 10 of Castillo-Corrales I. All the great rounds have two-way action and swings in momentum - but this fight takes it to the limit. Chico was as close to finished as you can possibly be, yet he came back to score the tko. It was so dramatic it almost defies belief.
That was a good one. Great ending! There are many rounds that will go forgotten because the fighters involved were not in the boxing elite. One relatively recent fight that springs to mind is Katsidis v Earl, I'm sure there was a round there that would be up there with those already mentioned on this thread.