AKA: Mister Machine. X-51. Aaron Stack.
First appearance: 2001: A Space Odyssey 8. (Now there's some trivia for ya!)
Powers: Machine Man has telescoping extremities, fingers that conceal a variety of weapons, and uses anti-gravity disks to fly.
History: The only one of 51 military robots to develop a "normal" personality, X-51 vowed to improve relations between humans and artificial life forms after the death of his "father," Dr. Able Stack. Many of his adventures came about because of his job as an insurance agent. He was a member of the all-robot team Heavy Metal and has teamed up with the Avengers. Machine Man's history tends to be a bit complex when you consider that at least part of it takes place in the future -- in 2020 he (or perhaps a facsimile of him built out of Machine Man parts that happened to be lying around) is scheduled to battle an industrial menace and search for his love, Jocasta.
Current status: Machine Man was most recently seen hanging around with the Avengers. Apart from that, it's apparently been very quiet at the insurance agency.