Anything produced by Trevor Horn. Welcome to the Pleasuredome still sounds awesome, as does A Secret Wish by Propaganda.
Even the new Robbie Williams record?
When I seen this thread my immediate thought was Year Zero by Nine Inch Nails. It's not NINs best work but it's a production tour de force, in my opinion.
I love Bill Stevenson and Jason Livermore. They've produced a significant number of my favourite records and are basically the go to guys for melodic hardcore. You could probably argue that the reason I like them is because of the bands he's produced, but their style is something I really like and I'd love to work with them one day.
Jimmy Page also deserves a mention. For obvious reasons. His production on the first four Led Zep records is great.
I have to be honest though, I don't often notice good production on records. In fact, I think that the mark of a good producer is that you don't really notice what he's done, just that they make the band sound spot on. I do, however, tend to notice bad production much more often.
EDIT: El-P is also great. I love the work on I'll Sleep When You're Dead.