10. HAL 9000 ('2001: A Space Odyssey')
Basic Function: To control the Discovery One spaceship by responding to voice commands. He's so trustworthy and reliable that nearly every aspect of the ship is under his command. (Some might argue that due to Hal's lack of a body, he's more a computer than a robot, but since he talks and has a glowing red eye we're gonna count it.)
Good or Bad: Very, very bad. As Homer Simpson once said, "Trusting every aspect of our lives to a giant computer was the smartest thing we ever did." Well, it wasn't true for the Simpson family and it certainly wasn't true for the astronauts on the Discovery One in Stanley Kubrick's 1968 classic 2001: A Space Odyssey. When astronauts David Bowman and Frank Poole try to disconnect HAL after he exhibits some strange behavior, he does everything in his power to kill them.
Boldest Action: After reading the lips of Bowman and Poole as they plot against him, HAL locks them both out of the ship. "I know that you and Frank were attempting to disconnect me," he says. "And I'm afraid that's not something I can allow to happen."