I'm not sure if this counts, but here goes.
Recently I took up Dwarf Fortress, an incredibly detailed simulator where everything down to the emotions of all your Dwarves are simulated constantly. Well I had just survived a lengthy siege, and though we made it out okay my Dwarves were not happy. Particularly unhappy was my max-level master Axedwarf, for the rest of this story I will call him by his randomly generated game name, Solun.
So, Solun has legendary level axe wielding, armor use, and various other combat skills, as well as high tier equipment. However, despite being a master warrior, Solun is also afraid of insects.
Now, during the siege we had to survive exclusively on food stores, and had to ration food. No one was happy, add in combat stress from the military dwarves and you have a time bomb (yes, Dwarf Fortress DOES simulate that).
So, normally I keep cats in the fortress to kill off vermin like mice and roaches. However, because of the siege they had to be caged so that they would not be risked being killed by combat (Cats, unlike other pets, choose owners for themselves rather than the other way around, and losing a pet causes significant depression in a Dwarf, which I absolutely did not need while my fortress was under siege).
The siege is over, and I can finally end rationing of food. So people begin eating like normal again, ie by bringing all their food to the dining hall and gathering and generally (at least I like to assume) having a good time. Among them is Solun.
Remember how I said that Solun is deathly afraid of large insects? Remember how I said that the cats were caged and hadn't been let back out yet and so could not kill off vermin and insects? And how everyone is gathered together in a small place in the presence of an unstable weaponmaster equipped with high-level gear?
Well, along comes a couple cockroaches. Solun completely flips shit and throws a tantrum, killing a number of Dwarves in only a few minutes. This greatly upsets a number of the other war wear Dwarves, military and otherwise, who then proceed to throw their own tantrums and begin attacking each other.
At the end of it, the appearance of a cockroach at the wrong time caused my population to be reduced from 124 to 16, 4 of whom were permanently crippled, and another 7 had to be hospitalized (miraculously, the doctor had not been severely injured in the fight).
Not a rad roach, not a mutant super cockroach, by the way. An ordinary cockroach that normally only exist as playthings for my cats.
It wasn't a loss, but it was a significant setback that I did, fortunately, manage to recover from.
By the way, I'm not at all upset about this. Learning, largely through failure, is a part of the Dwarf Fortress experience (the game's motto is "Losing is Fun!"). Plus it's kind of a funny story.
Also, I highly recommend anyone with the time check out Dwarf Fortress. It is completely free and donation supported, and runs in Windows, Mac OS X, and Linux, and requires very little computing horsepower to run (the default game uses ASCII characters for everything, but there are graphics packs you can install. I highly recommend getting the Lazy Newb Pack if you try DF). Though reading the wiki is basically essential, it is well worth it to do so, and it is also very well written and readable and quite humorous in many cases.
