I wasn't sure whether to enter this jam, but my other project is a bit stuck. Then I thought, what if you could fish with a grappling hook? And so: F!shing
Idea: Side-on platformy controls. Use your fishing-related earnings to buy better (or just different) equipment. And a boat! Boats are good.
I'm hoping to have a Worms-ninja-rope feel to the fishing rod, swinging it wildly trying to get fish with it. Other equipment will vary as I come-up with ideas for it. But definitely a grappling hook will be one.
Depending on how early I finish, I might also add an end-of-year tax-return minigame! Because you have to report fishing earnings on those. YAY!