Super famous, everybody's seen him but nobody knows him

I know who he is! He played "Peewee" on St. Elsewhere. I think he was just in two episodes, and he simply lit up the screen! There aren't very many actors as talented as he is. He should have gone farther, but Bruce Paltrow is a jerk among jerks.

has he ever gotten an oscar nomination?

He's not a household name, but people know him.

I know him from Max Headroom, Star Trek, and the Sherlock Holmes movies he made in the early 2000s.

Off the top of my head, M-m-m-max Headroom! Holy crap Amanda Pays was a major early crush. Also he was the Trashcan Man in the Stand TV mini-series and Moloch in The Watchmen.

On looking at his IMDb credit page, he seems to be doing alright as a working actor.

I've known who he is since the first days of Max Headroom. Always entertaining.