Golden Heat Seeking Bullet Bills are sub specie of the Missile Bill, which is a sub species of the Bullet Bill.
They have only appeared in one game, Super Mario Sunshine. They will hopefully be re-added in future Super Mario games.
Super Mario Sunshine
Golden Heat Seeking Bills appeared in few missions including the final one. They're purpose is not only to follow and damage Mario, but to provide up to ten coins upon their defeat. Golden Heat seekers are usually accompanied by two or three Heat Seeking Bullet Bills. They have a strange smiley face on them sometimes.
- Golden Heatseeking Bullet Bills drop coins upon impact with Mario or a surface.