Customize a weapon.

Increase your inventory slots.

Open a portable safe.

Combine two items together.

In Voyage of Despair, acquire the Sentinel Artifact

Reach Commander (Level 55) in Multiplayer while playing online

Earn 10 medals that are based on Special Issue Equipment

In Blackout, unlock Battery, Ruin, Firebreak, Seraph, Nomad, Prophet, Ajax, Crash, Torque and Recon

Kill Mom's Heart 5 times

Have 7 or more max red hearts at one time

Beat 2 levels in a row without picking up any hearts

Beat the Basement/Cellar without taking damage

Kill Satan with Azazel