Just me thinking out loud, but here is my list of some the greatest rap duos or Groups in no specific order:
Outkast
EightBall and MJG
UGK
NWA
*Jazzy Jeff and the Fresh Prince
Wu Tang
Dougie Fresh and Slick Rick
*Eric B and Rakim (DJ and Rapper)
The Fugees
Public Enemy
Two Live Crew
Grand Master Flash and the Furios Five
Sugar Hill Gang
Who do you think needs to be added to the list??!!