Mine was similar to Bill's, which is my 1/4" plywood surface on top of the work bench. I cut on it, mix paint, store things, it's a jig, cleans the crusty stuff of my putty and glue tubes (I still use it for some things), it's s straight edge, and a friend.
After that would be old #11 blades. If there was one tool that is indispensible this is it. Before we stole our mom's tweezers and had fancy tools like sprue cutters and etchmates, all we had were hobby knives.