First of all, it's easier if you set control bindings to default. This guide will ONLY use bindings to default, SAVE FOR THE TAB BUTTON!!. As we all know holding shift and tab on steam brings up the community. So Set tab "stats" key binding to something else. Also first person button conflicts with another button, so we gotta change that too.

---To simplify---
Default your controls.
Change Stats to R
Change first person to G
Do these codes super fast with game NOT paused.

You NEED to hold down "Left Shift" and "Right Mouse button" (at the same time) while entering these codes as fast as you can. Then release. Slow button pressing will not work.

All Psi powers
X, X, F, E, [R], F

All Psi powers upgraded
[R], [G], [R], E, X, E

Full ammunition.
[G], Space, [R], [R], F, X

Full arrowheads.
Space, [G], [G], E, F, Left Mouse Button

Full lives.
[R], E, E, X, Space, [G]

Global items except for Psi Colorizer and Dream Fluffs.
[G], X, E, E, [R], F

Anything with [ ] is something you had to have changed.