Assuming most people don't know what it is, have a ridiculous guess.

A-Team I: 200% energy bar + 3rd weapon slot
A-Team II: Bonus Damage resistant Mohawk
A-Team III: Helicopter Call in for 1 minute once each game

Just a bit of fun around the forums.

I am guessing it is an error and it does not exist. Just as initially when the game was launched it said there were 29 weapons when there really are only 20. If you really want to know, message one of the players who have already boosted to 5th prestige who are at the top of the XP leaderboards.

Boosters = Losers