I can't stand invisible ambush parties. I'll spend forever building intricate defenses of dodge traps, fortification, rooms full of armored war beasts and golems, but then usually never open my front door. I end up letting the caravan guards deal with ambushes the best they can.
I've only ever seen one hill titan/forgotten beast that wasn't a complete pushover. It was made of cloth, immune to lava and all combat, and spammed webs like there was no tomorrow. The rest of the beasts I've seen usually die from a wardog or untrained miner in a few hits.
I read old fortresses like Boatmurdered and long for the days when the game was completely unforgiving and was more prone to insanity like that. I've never actually experienced the dreaded tantrum spiral, a herd of deadly elephants, or seeing my legendary fighter going insane. I also miss the vanilla catsplosion for their delicious meats and being able to drop them and let them splatter in the grand hall to get all my dwarfs used to the sight of death.
I've never ever set up a metal industry using coal. I found metal to take far too long anyways so even back in my first games of vanilla I focused entirely on a lava industry. That being said I have never successfully set up a pump stack. I usually just end up having my dwarfs run up and down a hundred flights of stairs at a time.