The Sidewinder Revolver and the Ranger Assault rifle are available from the start of the game, any other weapons have to be unlocked by visiting certain locations on the map. In total there are currently 8 weapons on offer in Rage 2, once you have tracked them down you need to approach them within the actual Ark and hold down the X (Xbox 360) or Square (PlayStation 4) button on your controller. Upon doing so you will be taken to a training area wheree an AI will take you through the steps of using the weapon against enemies. Below is a list of the different weapons in Rage 2 along with a brief description and where you can find them.
Sidewinder Revolver
Location: Unlocked at start.
This revolver deals decent damage with low recoil, it doesn't have an alternate fire mode.
Ranger Assault Rifle
Location: Unlocked at start.
This assault rifle deals solid damage with good range, it doesn't have an alternate fire mode.
Firestorm Revolver
Location: Dank Catacomb Ark
This revolver fires mines which can be manually detonated. It can also fire off mines that detonate immediately on contact.
Combat Shotgun
Location: Ark underneath Gunbarrel (story-related)
This shotgun fires strong pellets at a slow rate. It can also fire a wide horizontal line of pellets.
Hyper-Cannon
Location: Greenhaven Ark
This high powered railgun can pierce through multiple targets. It can also fire a powerful beam that punches through targets.
Smart Rocket Launcher
Location: Strongbox Ark
This powerful rocket launcher fires individual missiles. It can also lock onto targets and fire homing missiles.
Grav-Dart Launcher
Location:Needle Falls Ark
This weapon inserts needles into a target and then throws them around.
Charged Pulse Cannon
Location: Shrouded Vault Ark (need to complete Shrouded Sub Station Alpha and Bravo first)
This weapon fires a charged laser beam that incinerates enemies.
BFG 9000
Location: Meteor Crash Site
This weapon fires one huge ball of energy, it doesn't have an alternate fire mode.
Check out our How to Unlock Vehicles page to find out how you can unlock the various types of vehicles are that are in Rage 2.