M56 Smart Gun

The M56 Smart Gun first appeared in Aliens (film), the second film in the series. It is significantly larger than the M41A Pulse Rifle and serves the role as heavy fire (as if the Pulse Rifle isn't heavy enough!) in the Marine Corps.

It is "smart" because it can lock onto a target and follow it robotically while firing. Obviously such complex moving parts make the gun quite large and it attaches onto the shoulder and back for support and stabilization while using.

The Smart Gun appeared in the video game Aliens versus Predator 2, where it could lock onto enemies but slowed the run speed of the person using it due to its weight. Often it is disabled in multiplayer matches due to an opinion that it is overpowered.