Descent: Freespace for me; it was my first try at the final mission, where you have to destroy five generators on the SD Lucifer superdreadnought before it completes its jump into Sol system and devastates the Earth. I'd lost all my wingmen knocking out the first four generators, my shields and armour were down to critical, and I released my last Harbinger bomb at point-blank range and hit the afterburners to escape the blast radius just as the clock was winding down to zero.
It was so close that at first I thought I'd failed the mission - then I got the successful ending cutscene.
All in all, not a bad way to finish a game off, especially with a roomful of friends watching over your shoulder.
