Sportin' Life in the original cast of opera Porgy & Bess. The released rehersals of that cast (with Abbie Mitchell's Summertime) don't include It Ain't Necessarily So. The first version on record was by Laurence Tibbett, white singer who cut a few selections for RCA a few days after the première in Boston, with Helen Jepson, George Gershwin and original conductor Alexander Smallens and his orchestra.
Cab Calloway [on Broadway]
Sammy Davis Jr. [in film version]
Finlay Quaye [on Red Hot + Rhapsody]
See also: I Loves You Porgy and of course Summertime.