I think it's great that the theme is 'Supernatural'. As someone who has watched all 15 seasons of the adventures of the Winchester brothers I believe there is a lot of potential there, so kudos to whoever decided this tv show should be the focus for this game jam.
I'm thinking a side scrolling survival horror game, where you play as Sam or Dean and they have different abilities, like: Dean can actually emote properly and Sam has the capability to gurn in a facsimile of being a better actor. You rummage around the environment to find rock salt for ghosts, or silver jewellery / cutlery that you can melt down into bullets for killing werewolves. Smash up chairs / tables and sharpen the wood to make stakes for killing vampires. Draw spells using the mouse in a manner that may, or may not, be totally cribbed from Arkane Studios "Arx Fatalis"
This game jam topic is a really good one