This guide will show you the code for the keypad.
Where to Find It
The location of the keypad is on Abyss. Go to the left corner of the map. Scroll your mouse wheel on the corner. Then you will see this:
You click the buttons with the drag tool. Also, this picture will help you with what the numbers are.
The code is 628 318 530 717 95. If you mess up, then just click random numbers until it says Incorrect. Then it will restart. This is what it should look like when you did it.
Warning: I think you have to have uncharted territory unlocked for this to work. What the keypad does: I think it adds the Normal Sized Gun to your spawn menu.