Past: gotta agree with Douglas > Tyson
Present: been a few but i'm gonna go with Hopkins > Pavlik... He had been written off by virtually everyone, and Pavlik was a bit of an unknown quantity with supposedly only the sky as a limit.
De La Hoya being beaten by Pacquiao had been predicted by quite a few smart people (myself included

) and Mosley beating Margarito had also been predicted by quite a few knowledgable people (myself not included

)
Future: I see Juanma Lopez's world coming crashing down at some point. However I'm not confident enough to venture a name