Gunslinger Stratos (ガンスリンガー ストラトス) is a 4 v.s. 4 third-person shooter arcade game came out in 2012. Every character in this game is equipped with some type of dual weapons. During the gameplay, players can transform their dual weapons into speciality ones based on situations such as a machine gun for rapid fire or a rocket launcher for more power. My favourite part is that these weapon transformations are initiated by combining the physical lightgun pieces in different ways.
Combine for more power 
Combine for rapid fire
