Railgun

A railgun uses electromagnetic rails instead of chemical propellants to fire projectiles; this allows the rail gun to launch shells at extremely high velocities. A portable version is used by Fortune in Metal Gear Solid 2; however, man-portable railguns are entirely fictional and do not exist in real life. A larger, more plausible version was used by Metal Gear REX. While REX's designer originally intended it to shoot down nuclear missiles, it was refitted to fire nuclear warheads instead. There also appears to be one mounted on Crying Wolf's back, which also lowers into a sniping position for more ease while aiming as seen in Metal Gear Solid 4: Guns of the Patriots.