Ledger was also in "The Patriot" as the oldest son of Mel Gibson's character. He turned in an excellent performance in that movie, which if you only see about one movie a year is the movie you should have seen about 8 or 9 years ago.
He’ll be know by the end of this year as The Joker just as Brandon Lee became known for The Crow which was posthumously released.
The studio already put out a clip from the new Batman film to cash in.
As it stands now, he’s previously known for a film that few people actually saw (his character’s name isn’t mentioned, he’s just “one of the guys from...”).