X-Com: UFO Defense (UFO: Enemy Unknown)
I used to play this game all the time back in the day, and I would always get stuck when it was time to start taking down large UFOs and enemy bases. However, last night I recovered the first "very large" UFO of my career, and I did it without any casualties! I even captured a Snakeman Commander, which is something I've also never done.
Granted, there weren't any mind control aliens on the ship... I know this is going to be my undoing, like always. One mind control alien ALWAYS destroys my entire force. We'll see.