BioWare's sprawling space opera was the ultimate fan service to Star Wars lovers. It was also a damn good RPG filled with memorable characters. But as anyone who has ever played it knows, the pivotal moment in the game was finding out that Darth Revan -- responsible for all manner of atrocities across the galaxy -- was actually... you.
Since your mind had been wiped and then brainwashed to the Light side by Bastila, the twist came late in the game and ultimately led to a choice of agreeing to help defeat the Sith or ousting the current leader of the Dark side, Malak, and taking his place. The revelation was unlike any that BioWare had offered up before, and it secured KOTOR's place among the greatest RPGs ever made.