I'll admit early that he's not really "unknown" but at least underknown (in the US) -- the name is, of course, Ed Motta. He digs into some of the deepest dirtiest grooves, and has at least one ballad I like. I don't enjoy the early albums (too 80s, too drum machiney) but the later albums have some incredible tracks. My favorite of his albums are AOR and Poptical.
Some songs to consider:
Marta (AOR, extremely grooving)
Eu Avisei (Poptical, grooving)
The Rose That Came to Bloom (Poptical, ballad)
Dez Mais Um Amor (As Segundas Intencoes Do Manual, groooooovin')