I was going to say Corrales, only the one time he stayed down, against ano overweight Castillo perfect left hook.
First that comes to my mind is Joe Louis. He got knocked down a lot even againest opponents of lesser caliber, but always came back to put some hurtin'.
No-one ever actually knocked Razor Ruddock out, if I remember correctly. He wasn't particularly easy to knock down, but when he faced a big puncher, he would visit the canvas at least once. He could take a lot of power-punches and be made to do very strange things with his legs if you hit him hard enough, but despite his lack of defence and durability he was never cleanly knocked out.
Neither qualify by the remotest stretch of the imagination. Patterson was down a lot but generally got up,Louis too. Recent smaller guys ? Corralles and Trinidad.
Danny Lopez, Prince Naseem Hamed immediately come to mind. Best display of it I've ever seen is Carbajal vs. Gonzalez, GOnzalez is battering him in a close fight and drops him heavily TWICE. Carbajal comes back and absolutely destroys him, what a fight and what a comeback.
Aaron Pryor- Got dropped early on more than one occasion. Also the same with Felix Trinidad. But both always roared back later on. Bobby Chacon would always come back strong.
He was talking about Brian Vera, and the way Codrington dropped him in the Contender Series III and he got up, not Codrington being a fighter who gets knocked down but always gets up.
carl thompson deserves a mention, was only knocked out cleanly once, but was put on the floor a fair few times. And you may laugh but David Haye has never been 'knocked out', but has been floored plenty of times. Hopefully this doesn't change in the near future