Ok, I know that a rigidbody normally takes into account all the colliders that are child objects to it; how would i make it so it made exceptions/ aka. ignored a certain collider when doing physics so it has no influence on the rest of the rigidbody?
You want to use Layer Based Collision Detection. You can read more about it here: http://unity3d.com/support/documentation/Components/Layer%20Based%20Collision%20detection.html
Mmhm is playing with ignore layers and the ignore matrix is not an option, the only solution that comes into my mind is to work on the GameObject hierarchy so the ignored collider ends up not being a child of the rigidbody.