91 Rimworld: The game where random groups of people show up for some reason, and then just murder each other on the spot.
Edit: Also reminds me of Dwarf Fortress's "civil war bug". Basically, if you order your military to attack dwarven merchants from another fortress, they (your military) will be me marked as enemies of Dwarvenkind, but still somehow loyal to your fortress (and, as such, you can still order them around). Then, if you have a citizen militia, they may attack the separatist military dwarves, be marked as enemies of your fortress but still loyal to Dwarvenkind. The result? Anyone with a weapon will now go around murdering everyone in sight. The only solution is to somehow get all the dwarves with glitched loyalties away from your fortress and let them kill each other (or toss them into magma, etc.). For the original former-military separatists, it's easy, since they will still follow orders and you can just tell them to leave. The loyalists (dwarves who attack the separatists) are more difficult, since you can't just order them around. However, if they kill a citizen, they become renegades loyal to no one, and can then be killed safely. Or if you can trap them in a room and flood it with magma... that works too.
More info here.