Formula One Go-Kart Tracks
Formula One is one giant industry, and software companies make a fortune every year by selling F1 simulation games for PC or Playstation.
It would be fun to have real-life go-kart tracks that are small-scale models of the original F-1 tracks (Imola, Monte Carlo, etc.). I'm sure a lot of people would be happy to pay more just to get an authentic feeling when driving a go-kart. This should obviously be a chain of race tracks, either built in the original locations or even somewhere completely different.
Reward: Free rides for me and a couple of friends.