What weapons need to be found in the world rather than bought or unlocked?

Question

After buying every weapon available in weapon stores, I have found the U100 machinegun during the final weapon crate side mission. Are there any other weapons that need to be found in the world rather than being bought in a store or unlocked by completing various challenges?

Answer 1

As far as I know, there are no weapons that can be found outside of main story that can't be bought. Some weapons are unlocked and found by completing certain actions, like certain amount of mini-games or side missions or progressing through the story. You can see what weapons (and other goodies) are unlocked by completing certain actions in the progress menu.

Unlocked by completing certain missions.

• Spec Ops Goblin – Completing 9 weapons trades missions will unlock this weapon. A silenced assault rifle that shoots in bursts. Good for range and accuracy.

• Wildfire – Completing 6 missing persons cases will unlock this
  weapon. This weapon is a high powered and accurate assault rifle.

• Gangster – A Tommy gun unlocked by doing 17 QR codes.

• Chrome – You get this by doing stopping 20 crimes throughout the
  world. A high powered revolver.

• Destroyer – You get this by stopping 16 criminal convoys throughout
  the city. This is the most powerful sniper rifle but it only holds 2 rounds.