I'd have to say the cutting mat is what I use most. Blue side for cutting of course but, I use the white side for piecing and placing applique (so the glue doesn't get on my table or the cutting side of the mat). Aside from that I would be completely lost without my sewing box. So many things got misplaced before I finally bought one! Never will I underestimate the convenience of being able to find what I use most ;)