Nail Gun

An upgrade for the submachine gun that drastically changes the way it inflicts damage.

Advantages

 * Increased damage per shot
 * Wide cone of fire
 * Ricocheting nails can damage enemies around corners

Disadvantages

 * Ricocheting nails also damage the player, and are difficult to avoid in confined quarters
 * Inaccurate at long range

Strategy
Standing just outside an open doorframe and firing into a room from an angle shreds enemies before they can even see you.

Trivia

 * In real life, a nailgun is a construction tool that lacks the propulsive force to penetrate bone from a distance. The notion of a nail gun as an automatic weapon originates from the landmark FPS game Quake.
 * It isn't clear whether the Nailgun is a hitscan weapon that animates the trajectory trail or a projectile weapon with extremely fast projectiles.