The comments by Monroe Eskew and Andrés E. Caicedo concerning unpublished results of Hugh Woodin deserve to be made into an answer IMO. As a concrete example, Caicedo wrote:

There is the fact that Turing determinacy implies Suslin-coSuslin determinacy (in the presence of DC?), which gives L(R)-determinacy.

There are various other results by Woodin that may or may not fit the bill; in many (though maybe not all) cases, proofs have been provided by other authors. For more details, see Woodin's unpublished proof of the global failure of GCH and Unpublished works of Woodin on SCH and Radin forcing.