Cawl is asking you ideas for a new Space Marine organ idea, what will it be?
What new organ would you want him to create, and what sort of ability will it have? I'll go first, a Space Marine organ that allows for slow regeneration. Basically, anytime a marine loses a limb, they can grow it back over time while out of combat. It has to be something that's manually triggered by being injected with some sort of chemical compound.
Edit: two new ideas
An organ that's basically a circulatory system that exists only in the head, that works with the Sus-an membrane, in situations where both marine hearts stop working, it will kick in and keep the brain still going, it can't keep a marine conscious, only making sure the brain doesn't go brain dead.
An organ that allows marines to communicate using radio waves in short ranges. They can't communicate words, but can communicate certain thoughts, like orders to kill or targets they see. It can be a fail-safe for situations where the electronics stop working.