Well, off the top of my head...
UGK (basically everything)
Gangsta Blac
Kingpin Skinny Pimp
ESG
Fat Pat (just smooth...RIP)
Big Moe (esp. CITY OF SYRUP)
Lil' O
Lil Keke (but mostly his earlier stuff, like DON'T MESS WITH TEXAS)
The Botany Boys (and some of C-Note's solo's stuff)
Eightball and MJG
C-Loc (way underrated, and he's worked w/ some cool cats, too)
Lil Flip
Tela (especially his first two CDs)
Devin The Dude (I like both of his solo CDs)
Outkast (just about everything)
20-2-Life (their earlier stuff)
Three Six Mafia (but mainly MYSTIK STYLEZ, THE END, CH.2 WORLD DOMINATION--their more recent stuff sounds too much the same to me)
And of course, old Rap-A-Lot (Geto Boys and their solo CDs, Big Mike, 5th Ward Boyz, etc), pre-MTV fame Cash Money CDs ('95 up to about the end of '98 or so), and some Southern period No Limit (from early '97 up until Beats By The Pound left).
PEACE!