Probably a new short Assassin's Creed game. Imagine this: The year is 1506. You're the French assassin, Sebastian Valjean, on a mission to a spanish castle to assassinate the spanish templar Julio Gonzales. With your french troops you're attacking the incomplete spanish fortress Forteresse de Salses.
Of course you have the hidden blade, different kinds of swords, knives and poison, throwing knives, crossbows, and your fists. But since you don't know Leonardo da Vinci, you don't have a hidden gun, metal cestus or poison darts, but a musket from the Renaissance.
I think that game would be awesome.