Rigidbodies push other rigdidbodies

I am trying to set it up so that my character which has a rigidbody will not push a wall, which is also a rigid body.
I tried using, Mass, but I found that more Mass ≠ more Weight.
Is there a way to make a rigid body that cannot be pushed by another rigidbody?

As an example:
A car hits a wall and stops. Rather then, a car hits a wall and pushes the wall.

Set a wall to be Kinematic, or use a mesh collider and set it to ‘static’

Or perhaps try this:

http://docs.unity3d.com/Documentation/ScriptReference/Physics.IgnoreCollision.html

Or place the objects on different layers and clear the corresponding box in the collision matrix.