Pete Rock
Diamond D
Eddie F
DJ Premier
Lord Finesse
Daz
Quik
Rick Rock
Fredwreck
DJ Slip
Battlecat
Big Hutch
Nick Wiz
Jesse West
Large Professor
K-Def
DR Period
Terrace Martin
Dontae Winslow
Cardo
DJ Khalil
DJ Pain One
Sounwave
DJ Dahi
KLC
Hi-Tek
Lt Hutton
Daz Dillinger
Buddha
Johnny J
T-Mix
Pimp C
NO Joe
Dame Grease
P. Killer
Lil' Jon
Don Quan
Organized Noise
RZA
DJ U-Neek
Mannie Fresh
Alchemist
DJ Yella
Uncut Productions
Just Blaze
The Legendary Traxster
Damon Elliot
Stephen Marley
Battlecat
Scott Storch
DJ Premier
...that's all I can think of off the top!
I'm going to add a few more just personal favorites I felt really made me approach beat making differently.
I know somebody said Daz Dillinger already so I'll leave him out.