Suppression Device
The Suppression Device is a machine used in war-torn City 17 to obliterate nearly anything. Only one is ever seen, on the top of the Nexus Building.
It shoots a ray of energy(?) powerful enough to kill humans instantly. Luckily, Gordon is quite well-armored and can survive a number of hits. The device attempts to aim ahead of moving targets due to a small delay between firing and impact time.
The device can be deactivated by disconnecting multiple power sources. It's not clear if the device is operated manually or automatically.
See also
func_tankmortar
, the entity used to create one.