Here is a model of the CR25 Hyperion, one of the weapons in the DEADULUS mod for Half-Life.
..A background to the gun - It is the standard issue weapon for the crew on board the Deadulus space frigate. They are mass produced on earth and delivered to star bases around Earth.
The gun consists of a 20mm barrel for either armour peircing plasma rounds or conventional bullet projectiles and a secondary launcher attachment at the gun's top which deals a burst of superheated propellant which instantly ionises air in the immediate vicinity, annilating any biological target at point-blank range. Ionisation shielding must be worn to use this weapon. This will discharge the entire canister, however propellant can be controlled and used similiarly to a blow torch for other tactical situations.
At the side of the gun an ammunition indicator will indicate remaining plasma or bullet rounds. Other attachments are planned for the gun, such a scope attachments, other launchers etc.
Wow, thats a sweet model :D