A company called System Service is making Mega Man cosplay easy (and cuddly) with this pair of plush arm cannons styled after the Mega Buster and Proto Buster (Rock Buster and Blues Buster). These fit over your forearm to transform you into a super fighting robot! These are coming out in November 2013 for 2,400 yen each.

They can be preordered as a set at Big Bad Toy Store