There are various NPCs in the game that can offer services and bonuses for players. Here are a few of the important ones:
Muenster appears in every Home City. Visit Muenster to purchase or sell equipment as well as to exchange for gems or other valuable items. If you accidentally sell something click Repurchase to buy it back. Please note that an item will only stay with him for 48 hours. Don’t think Muenster can help you store things forever!
Visit the Ammo Cache to purchase guns, different guns have different level and Honor requirements. Higher powered guns will cost more.
Visit the Mysterious Merchant to get precious items such as Gene Diagrams and materials for Gene synthesis. He also sells Gems which you can socket in to your equipment.