If the tools let you make your own complete game I would make....
1. A Ganster themed FPS with 1930s streets filled with 1930s cars and gangsters to hunt down/avoid.
2. A Western themed game with horses to avoid being trampled over and other cowboys in the town to avoid/kill with lots of buildings/stagecoaches to use as cover. A sort of reboot of Boot Hill called Reboot Hill
