Here's some I didn't see on here:
Ant Banks (WC, Mack 10, E-40, Dru Down, Spice 1, etc.)
Big Saccs (Mausberg, Suga Free, etc.)
Bosko (E-40, Richie Rich, C-Bo, etc.)
DJ Glaze (Foesum)
Don Juan (early Tech N9ne)
Icy Roc (early-mid Tech N9ne)
Kay Gee (Naughty By Nature)
Sir Jinx (Ice Cube, Too $hort, Xzibit, etc.)
Soopafly (Snoop, Daz, Warren G, Kurupt, Eastsidaz, etc.)
Out of all of those, I'd say Soopafly DEFINITELY deserves his props, he did so many killer tracks, "Who Got Some Gangsta Shit" off the Murder Was the Case sdtk., "Welcome Home" off Jurupt's Streetz is a Mutha, "It's That Time Again off Roscoe's Philafornia record, "My Momma (Ola Mae)" off Warren G's I Want It All record, etc.