All my forts so far were abandoned due to FPS, or just abandoned, but I had some funny mishaps.
"Surely ten war animals, including an elephant, a cheetah and two bears chained by the entrance will be enough to stop that squad of bowgoblins if they decide to come inside."
A few salvos of arrows later the animals were wounded or dead, so I've sent militia with crossbows. "What do you mean, you have no bolts? I ordered 30 stacks last year."
"I have enough crossbow bolts, there is no need to waste more resources making them."
"I will make a civilian defence force and zerg rush the invaders." That one actually worked, but those civilians were frequently replaced by migrants.
"I will surround my entire map with a wall and build eight 10+ z-level dodge-me traps. This should give me a complete safety on the surface" Except some of my military were stupid enough to go fight goblins on 1 tile wide catwalks and dodge sideways, and friendlies caught by ambushes outside my walls were screwed.
"I will just keep mining, smelting, farming and making items. FPS? Pft, who needs it."
"Pentium 4 is a fast computer. Surely it can handle this game easily."
"If I spend 300$ on computer parts, including a better power supply and lots of fans, I can overclock my Core 2 Due to give me all the FPS, I'll ever need."
"Atom-smashing or giving away items is wasteful. I'll just hoard them all."
"I will just put some cage traps here." The leader of a bowgoblin squad got caught and his buddies sticked around. Later my animal stockpile kept growing until I figured that I can build a cage and link it to a lever or try to transfer a prisoner to a cage.
"I will transfer this deer to this cage." It broke free, and was running around my fortress for a long time, causing job cancellations spam, and making my military look like a bunch of morons.
"So what a few wild animals are running around my fortress unattended. I don't need to give a kill order. Some soldier will find them eventually. How much trouble can they cause." Turns out, just a lot of job cancellations, but watching animals and dwarves running away from each other, or military trying to catch something faster or crossbow dwarves spraying bolts around was hilarious.