I just found out that a few key combinations which are not assigned in the control options actually have an effect in the game, I've already found two of these, though I am unsure wheter or not there are more.
They are kinda annoying when you don't know about them, Unfortunately I already managed to crash a chopper and literally break my characters spine with them.

These are the ones I found:

Shift+W in a Helicopter: Makes your helicopter dive down.

CTRL+E/Q Makes your head's X-axis spin in a strange way. (Looks like the character breaks it's own spine.)