The Tactigon may actually be sentient. When bonded with K.I.A. he revealed that the Tactigon has the ability to feel fear.
The tactigon is an alien weapon. It's original wearer crashlanded on Earth.
Armory ( Violet Lightner) was talking to a consoler, telling her about how she and the Tactigon come intertwined. Armory tells her story. It starts off with her being depressed, and deciding to end her life by jumping off of a bridge, as she is falling, she says that she feels completely empty. "Then I felt something else. Like a consciousness... touching mine. And that emptiness... was exactly what it needed. I didn't know what it was, this... THING wrapping itself around my arm. But IT knew. And it knew what I needed. It's not like it spoke to me or anything. But somehow I understood what it was. A weapon, from somewhere else... that could become whatever its wearer needed the most. And what I needed most in my PERSONAL battle... was a reason for being. I got one. Helping people..."
The Tactigon turned itself into a grappling hook, and wraps around one of the beams on the bridge, pulling Armory up, preventing her from dying. It appears that before this event, the Tactigon has been lying at the bottom of the bay, waiting for a "empty" host, to come by, for it to overtake.
After that, Armory uses the Tactigon to help people, and deliver justice to the bad guys. She then uses her Tactigon, to join the Avengers Initiative.
In a training simulation, an incident was caused by Trauma using his powers to show Armory's fear; causing her to blast randomly trying to attack her fear, killing MVP in the process. Gyrich orders the Tactigon to be removed from Armory, and kicks her out of the Initiative.
After it is removed, and a fifth MVP clone is made, the Tactigon was placed on that clone, in an effort to make an unstoppable being. It binds to the MVP-clone, and then the clone goes insane, and becomes known as K.I.A... K.I.A goes around the base causing death and havoc all around, killing those who witnessed or had involvement in MVP's death. All this time, K.I.A is using the Tactigon. At one point, Trauma turns into the thing the Tactigon fears the most. (Some sort of alien) Thus, it is believed that the Tactigon has some level of intelligence.
The Tactigon's powers appear to be unlimited. Government officials classify it as a "Omega-level weapon." It has the ability to turn into whatever weapon the wearer needs, to accomplish the mission.
Those who have worn the Tactigon include: