Regina's starting weapon at the beginning of the game, in the game Manual it says the weapon is a "Standard 9mm handgun". This weapon is completely fictional. Most of it's overall design seems to be made from a mixture of the Desert Eagle, Glock 17, Heckler & Koch Mark 23, and Browning Hi-Power MK III.
Serbu Super Shorty
The dead drug store clerk in the Edward City chapter can be found in-game with what looks like a Serbu Super Shorty laying next him. It can be identified by its extremely short barrel and vertical grip.
Franchi SPAS-12
A Franchi SPAS-12 shotgun is TRAT Special Forces team leader Lieutenant Dylan Morton's weapon of choice.
M16A2 with M203 Grenade Launcher
M16A2 rifles with M203 grenade launchers are standard issue among TRAT team members. Accompanying SORT agent, Regina, also uses one. Despite its prominent use in the opening sequence, it is unfortunately never available for player use.
AR-15 w/ wood furniture
AR-15 type rifles with wooden handguards and buttstocks can be seen inside cases in the Drug Store.
Type 69 RPG
A Chinese Type 69 RPG is fired at the Tyrannosaur during the base attack by TRAT team member David Fork, distracting it (and destroying its left eye) long enough for Dylan and Regina to avoid becoming the main course.
Heckler & Koch MP5K
Shown wielded by Regina in promotional art and usable akimbo style by her in-game are dual Heckler & Koch MP5K submachine guns loaded with 15-round magazines. The in-game MP5Ks, unlike those in promotional images, lack vertical handgrips.
FN M249 SAW
The M249 SAW appears as the Heavy Machine gun in-game and is a Regina only weapon and features an odd looking thumb hole stock. Two normal M249 SAWs are seen mounted in fore and aft pintle mounts on the Jeep commandeered by Dylan and Regina when they're attacked by two angry Triceratops.
Walther WA 2000
The Walther WA 2000 appears mocked up as an anti-tank rifle minus a rifle scope and with synthetic furniture instead of a wooden stock and fore grip. It is a Dylan only weapon and is suspected to be of .50 caliber, judging by the size of the spent casings.
M47 Dragon
The M47 Dragon, usually used in a stationary position is mocked up as a portable anti-tank rocket launcher. Used by Dylan and David, it's the most powerful weapon in-game.
The HK69A1 is made up as a Flare gun in-game called the Signal Bullet. It is used during the Allosaur Nest and is used by both Dylan and Regina to signal for an artillery strike.