Ghorpm: Warcraft 2, human campaign, Grim Batol mission. And BTW: there is a third catapult even farther south ;)
ZFR: What else. And an extra point for remembering the mission name. :)
I knew there was another catapult further south, I just forgot that the first location contained two of them already, so you're right 3 in total.
And they were useful against the cannon towers, so losing men (or at least health) to get them is worth it.
The movie showed the stolen catapult destroying a zeppelin, something not possible in game.
Your turn.
You can't forget such an epic experience as Warcraf 2 ;)
Here is the next one:
I can't produce enough food so I have to import some or my people will abandon me. OK, no problem, I just have to arrange a trading route, build some trading facilities and everything should be fine. But... it's not! Traders are coming to my city and then they complain that their journey was in vain because I don't want to trade with them. WTF?! Take my monies and give me your food already, what's wrong with you guys?! I didn't even set a limit you can trade as much as you want! (long frustration period). Damn! Food is stored in granaries but it can't be delivered there directly during a trade! I have to set my magazines to accept food and only then I can trade. Duh!