What's the Attack Titan unique power? Honest question, I thought stubbornness was his main treat. He doesn't seem to have any special treat besides that.
I think the Attack Titan's power is being able to deal great amounts of damage even when being very damaged.
And I think this exact second, in which some red thing goes through his body has something to do with the power.
Here too, https://youtu.be/JFw52lj5Z6c?t=4m28s
Or maybe the power is just to be multipurpose. Or being able to unlock the "frenzy mode" from the pic on the previous page.
Still, maybe it's mystery is yet to be revealed. There must be another reason for the show to be called Shingeki no Kyojin besides that being Eren's titan.