Saki Amamiya (サキ・アマミヤ) is a character from the game Sin and Punishment: Successor of the Earth. His main weapon of attack is the Dolphin Gun, a gun / beam-sword hybrid which he uses to slash and shoot with. He makes his appearance as an Assist Trophy due to strong demand from Japanese gamers. This is similar to Marth's Dancing Blade. 
Originally a Japan-only N64 title (though with English voice acting and Japanese subtitles), Sin and Punishment is now available on the Wii's Virtual Console in America.
A member of a rescue group that hunts aliens known as Ruffians that prey on mankind. He's killed by Ruffians, but the advance scout Achi resuscitates him, and he gains remarkable physical prowess and becomes the hunt leader. During a battle, he transforms into a Ruffian, and his companion Airan helps him recover. He's optimistic and copes well with danger.