This list shoudln't be longer than one of delicious English food courses, but there are a couple... Douglas (his perfomance of Tyson is almost as school book as it gets), Tony Tubbs, Buster Mathis, Bowe, W. Klitschko, Lewis... Help me out here!
Jnr. also qualifies as well, I think, since he had very little going for him beyond his skill. Buster Mathis Jnr. had appaling conditioning, a dentable chin, little power and wasn't even particularly fast, but he had excellent defensive skill and counter-punching ability. People blame Tyson looking ridiculous against Mathis on Tyson's ring rust, but given how much better Tyson would look in his next fight against Bruno, I think a lot of it had to do with Mathis being an excellent- albeit unusual- technician.
Mathis Jr. gave Bowe problems too if I remember rightly. People say Tyson's timing was off because of the layoff. Maybe. But I figure Tyson also had a lot of difficulty because Buster was a good defensive fighter and was a small and low target. Tyson's style was geared towards chopping down big tall guys. If Buster had had a powerful punch he might have beaten Mike Tyson.