Video game plot twists and endings *SPOILERS*

#1
Due to my undying love of video games and such I decided to make a thread dedicated to storylines of video games. So in your opinions, what are the best plot twists and/or endings in any given video game? What are also the worst ones?

And please be sure to use SPOILER tags when you mention the twists or endings, mainly for those who haven't played the game yet.

I'll start with an early one. Remember Star Wars: Shadows of the Empire?

At the last level you fly in your ship into this skyhook thing and blow up the reactor, thus destroying the station but also yourself because you're trapped inside. However, if you set the game to a higher difficulty it turns out Dash Rendar (the player character) didn't die but just zipped off to lightspeed right before the explosion, thus escaping.