The logical conclusion to these "Lets improve what isn't broken" threads

Is to propose a game made with the specific purpose of being given away en masse.

So, this isn't a "Your dream game" thread. It's about what would be fun to giveaway on a Bad Rats/Fortix level.

My idea - Built in the classic Doom engine, this FPS casts you as a doctor during the bubonic plague. You are given an anachronistic flame thrower and tasked to kill all the rats in a Scottish castle. You'll also encounter plague victims who you must kill in mercy.