observe
Banned
MF Doom also
Havoc count?
All time list and then some current-day sleeper picks:
Pete Rock, Large Pro, RZA, Havoc, Lord Finesse, Black Milk, Dilla, Kanye, DJ Quik, Diamond D, Eric Sermon, Q-Tip...
Nottz is a really good sleeper pick also. Again, not a brilliant lyrical miracle dude or anything like that, but from a pure live show POV he should get some attention. Honestly, Nottz has some of the best breath control on a live stage that I've ever seen. Forget producer rappers...rappers in general.
You Need This Music was one of the more slept on albums in 2010. His raps are pretty straightforward (he mostly raps about how good he is at making beats) but he does it well.
People would probably expect me to put Alchemist as another sleeper pick in here, but I won't. He's my favorite producer but I don't love his raps. That Step Bros album though is the best he's ever rapped, and if he rapped like that on more albums I think he'd get more props.
Evidence is slept on, but most people don't think of him as a producer.
A lot of people really are into Madlib as a rapper. I'm not there yet. Same with Oh No.
I don't like Black Milks production
), but none of them ever spat bars like: 
I was more speaking of him as a rapper. His production to me is hit or miss. I dig his older stuff. Once he started doing so much live drums and live band stuff, I started liking it less overall. Tronic was probably the last album he did that I rocked with most of the beats on it. My favorite Black Milk project is Popular Demand.
And RZa didn't had GZA writing some of his verses?
He's one of the greatest yeah, but I can't say he's the greatest of all time. That goes to DJ Premier for me. But hey, production is ultimately a matter of taste.