Saul Williams is one - his roots are in spoken-word, but he isn't terrible as a rapper and he can carry a tune. The early-90s had plenty of rappers incorporating singing - Arrested Development and Bone-Thugz-n-Harmony (never mind their rapping ability). Also Lauryn Hill, Farrell, and Andre 3000.

They're not that hard to find, none of these are all that obscure.