The Sentient Armor is the Iron Man Armor Mark I.
The armor briefly gained intelligence in Man and Iron Man. Tony was upgrading the armor's exoskeleton software, but he had to use it without testing it on an upgraded Whiplash. During the battle, Iron Man suffered the impact of a fall which, a virus transferred from Whiplash to him and combined with the recent untested upgrades, made the armor sentient. When Tony used it again to try to find Whiplash's and Mr. Fix's lair, the armor suddenly took over. It smashed into their hideout and easily beats up the two villains, and (ignoring Fix's pleas) causes the lab to explode with a single repulsor blast, seemingly killing both Mr. Fix and Whiplash.
Tony and Rhodey decide that the armor needs to be taken care of. The suit craftily lures Tony away, and attacks Rhodey. The armor then decides that Tony's danger-seeking behavior is not healthy for him and tells him that he needs to be confined within the armor at all times. Tony resists and damages the armor. It tries to shoot Rhodey, who grabbed a repulsor gauntlet, and Tony jumps in the way of the blast. Tony's heart goes into cardiac arrest and the armor, due to its desire to protect Tony above all, uses all of its energy to save its creator's life, sacrificing itself. After that, Tony began rewriting its intelligence chips so his armor can never gain sentience ever again.
As an armor created by Tony Stark, it has all of the same capabilities:
- Superhuman Strength
- Enhanced Durability
- Energy Shield
- Sensor Systems
- The ability to divert its power to activate certain machines.
- Enhanced Speed