I like the endings where you think something terrible is going to happen, but then gets turned around by something cool happening.

To this day I've yet to find an ending that's given me a bigger smile on my face than System Shock 2.

After defeating the evil computer on the ship SHODAN, she lies in front of you. Throughout the course of the game it's made evident that she believes herself, a computer, is vastly superior to humans. Thusly she talks about how she doesn't understand how a simple human "albeit cybernetically enhanced" could defeat her. But then she attempts to make an ultimatum with your character. She's currently in control of a drive which can enslave the universe, and thusly ask you to join her, saying that the two of you can rule together...

Close up to your character's face - "...Na!"

He then shoots SHODAN in the face with a pistol, thusly owning her. He then contacts a shuttle which had been jettisoned with two surviving crew members, only for another scene to show one at the intercom talking before the other comes from around the corner, the outline of SHODAN's form showing she's been subverted into a cyborg with SHODAN's personality, leaving the first lady of Psychotic AI's laughing.



Then again, that's just me...