Some cost real world cash, others gold nuggets. All of them, aside from Bob Molechaser, make the game a bit easier:
Twinblade San ($4.99): He destroys both side obstacles with his blades.
Julie Braveheart ($4.99): She destroys wooden upper and lower obstacles with her sword.
Ace Upsleave (10,000 gold nuggets): Nuggets he collects are worth 10 percent more.
Axel Firechief (30,000 gold nuggets): He can break upper obstacles using his axe.
Daryl Plankbuster (50,000 gold nuggets): She can destroy left obstacles with her guns.
Charles Longshot (50,000 gold nuggets): He can destroy right obstacles with his rifle.