Some spoilers to follow...
In the third act of Stanley Kubrick's 2001: A Space Odyssey, astronauts Frank Poole (Gary Lockwood) and Dave Bowman (Keir Dullea) are on a mysterious mission to Jupiter. Their only companions are three other men in cryogenic stasis and the HAL 9000, the all-knowing, all-seeing computer nicknamed Hal (voiced by Douglas Rain). Hal, who is supposedly "incapable of error," really is like another crew member; he talks to Dave and Frank, plays chess, and even expresses some trepidation about their mission to Dave. No one knows if the computer truly has feelings or motivations of its own, but as the mission progresses, Dave and Frank begin to suspect something is going wrong with their comrade. When Hal alerts them to a problem with the ship that they can't find, Hal blames human error, but this makes Frank and Dave even more suspicious. Is Hal making errors, or is Hal developing a mind -- and a mission -- of its own?
Dave and Frank meet in one of the soundproof pods to discuss disengaging Hal's higher functions if the computer is wrong again, but they didn't count on the fact that Hal can read lips.
After Hal causes Frank's sudden, silent death out in space, Dave goes out in a space pod to retrieve his body but Hal won't let him back on the ship. Dave manages to get back in and heads straight for Hal's motherboard as Hal apologizes, promises to do better in the future, and begs Dave to stop. Even as Dave silently, even sadly, takes Hal apart, Hal continues to talk to Dave. Hal knows it -- he -- is dying, and he's scared. Hal offers to sing Dave the first song he was taught, "Daisy Bell," as his voice grows slower and slower.* Hal's voice never raises in anger or quavers with fear; it simply slows down until he dies.
Hal's awareness of his own death touches me deeply. In a way, it reminds me of the ending of Flowers for Algernon, when Charlie begins to return to his original state but still remembers the brief period of time he enjoyed as a genius.
* "Daisy Bell" was the first song ever sung by a computer. Listen here.