Nick Cave:
- Wrote the novel And the Ass Saw the Angel,
- Has released numerous albums with the Birthday Party and Nick Cave & The Bad Seeds, and
- Starred in the movie Ghosts… of the Civil Dead.
He also wrote the screenplay for the 2005 movie The Proposition, which starred Guy Pearce.
I’m not sure how close any of those come to the OP’s requirements of “best selling”, “number one” and “box office smash” (does anyone know if any of Cave’s albums have gone to number one in the UK?), but they’ve all been fairly successful endeavours. He’s a talented dude.