I've decided that I now want to play a zombie outbreak strategy/SIM game. One where you are the president of the US.
A zombie outbreak occurs in a random location in the world. You must use your intelligence gather resources to tell where it's coming from and how fast it's spreading. Then you must set up emergency plans to protect your own people, combat the threat, prevent it from spreading, evacuation, economy, maintain infrastructure, etc.
Or hell, give me a mode in Civ where zombie outbreaks can occur.
Edit: Heck, why just zombies? Any sort of sci-fi outbreak! That would make it more complex. Maybe it's an alien virus and if you nuke it, it spreads faster! You don't know what it is at first, it could be anything.