I gotta say Hi-Tek. JB, Alchemist, RZA, Dre, Cool & Dre, Neptunes...all of them are up there, but Tek is just a f-ing monster on the samples. I still maintain that "The Sun God" is the most impressive, intricate, and deep beat I've ever heard. Plus you combine the recent commercial beats he's been lacing for G Unit and others with his back catalog of great beats...ie reflection eternal...he's dope.
As far as my favorite recent producer, that would have to go to Nicolay who produced the Foreign Exchange album. If you haven't heard it, stop what you're doing, and go buy it (its pretty easy to find in any good record store or on iTunes). The emcee is Phonte (from little brother) and Nicolay laces hands down the best production overall on a CD I've heard since Dre's 2001.