It's not like it's impossible for it to legitimately be energybending. For example, maybe only the user/the victim see the lights, that wouldn't be too crazy.
Having said that, I personally don't believe he's really doing energybending. One of the cooler theories I've heard is that he's in cahoots with Koh and he's stealing a person's spiritual "face", leaving them unable to access their head chakras and bend. (Aang's enerybending worked through the head and the heart chakras, so this wouldn't be too insane. >_>) Even that idea is pretty out there though, but aside from that I don't have any really good guesses as to what it could be.
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Falcon Punch
http://www.youtube.com/watch?v=FFtw7qW7Vcw