Aww yeah, Robots. I love them. Here's my top 5:
Robbie the Robot from Forbidden Planet. A Three Laws Compliant robot build with the lost technology of the Krell, an alien species that disappeared under mysterious circumstances. Helpful, intelligent, and uniquely for it's time, not a rampaging monster.
It's not really a robot, more like a giant computer that fills an entire spaceship. I think it's close enough to count, and if I have to explain why he is such a cool robot, that means you haven't seen Space Odyssey yet and you should do that right now.
When the alien bringer of peace needs to back up his words with firepower, he brings out a robot that has the power to destroy everything, or give life to the dead. Perhaps the most advanced robot in fiction, save perhaps for my number one robot of all time.
Kryten is a humanoid robot from the distant future. His only joy in life is serving human beings, although when the Red Dwarf crew found him, only one living human remained in the universe. Exceptionally fussy, neurotic and, at times, very rude, he is the funniest and most lovable robot you've ever seen.
R. Daneel Olivaw, a humaniform robot from the Asimov novels. In his first appearance he teams up with Earth detective Elijah Bailey to uncover an interplanetary conspiracy. But he becomes increasingly worried about the future of humanity, and with the help of the psychic robot Giskard and a limitless supply of logic, he tries to overcome his programming so that he can serve humanity as a whole, even if this means taking actions that would violate the First Law of Robotics!
A gentleman, a scholar, and the greatest protector humanity will ever have, this robot is by far my favourite. Just talking about him on the internet does not do the great stories of Asimov any justice, so I'll stop now.