Playing most Zelda games for the first time is always a magical moment.
Other than that, there's a specific moment from when I was playing Act of War: High Treason. Man, this game was
hard. The Dark Souls of RTS.
Well, there was this one mission, where you have very little room to build your base, and almost no resources other than what you can steal from your opponent (the main source of income in this game once you've exhausted what was on the map is usually to capture enemy soldiers and put them into camps, but for obvious story reasons you couldn't do that in this mission), while said opponent has multiple bases, artillery, air force, you name it. Spent an afternoon on it without much progress, but at least from all my failures I knew pretty much exactly where was what.
So I took a few days and actually made a battle plan. Start going there, capture these vehicles before they can get them out themselves. Use those to destroy this base before they can send air support, then continue and deal with the control towers so they
can't send air support. Yadda yadda, then I booted up the game, loaded the mission, and did it without losing a single soldier.
I was like, now
that's what an RTS is supposed to be like... only to give up a couple of missions later as the difficulty was getting super frustrating.