Yeah it's RZA, IMO. Know it sounds cliche and redundant but if I said anyone else I'd have to add "besides RZA." He's one of those producers who can make beats that sound nothing like the songs they sampled from, and I really dig that. He also makes beats that are damn near impossible to sample.
Personally don't see what's so great about some producers mentioned like Kno or Kanye West. I like them alright but to me they're just ok.. not even top 10. People say Dre's overrated but look at Kanye. I happen to like Dre's G-Funk style beats.. although that's mostly cause I also happen to be a fan of old school P-Funk. New York beats sound so cluttered and abrasive.. which is cool but I also think it's cool to escape from that sound once in a while and Dre was basically the first to do it on such a large scale.. for which he has my respect. The whole high pitched melody and heavy bass accompanied by hedonistic rhymes... I love the G-Funk vibe. Really does a good job at continuing the ways of funk.