This is where i found out about it, was trying to grab some info from here and kept reading…
http://en.wikipedia.org/wiki/Street_Fighter
“Interestingly, the Hadouken ability appeared in Mega Man X and its remake Mega Man: Maverick Hunter X as a secret move for X. It is only obtainable by having all heart tanks, sub tanks, weapons, upgrades, and no damage on health. The input was the same as in Street Fighter. This move can kill almost anything instantly, with the exception of several bosses. Even these, however, could be killed with two Hadoukens.
Also, Hadouken is the name of a beer brewed by a local Twin Cities brewer.”
all the info thats given, i googled but couldnt find anything else.