The SIG Sauer P226 is a semi-automatic pistol designed and developed by SIG Sauer. It is a very common sidearm to be issued to various militaries and special operations groups throughout the world. It's also seen action with various law enforcement agencies as well.
In Mario Warfare, Luigi is seen chambering a SIG Sauer P226 pistol before taking up an M-60E3. He however doesn't use it because he doesn't go with the others on account of his physical injuries he sustained from the Hammer Brothers.