I did some ruler work on my " almost forgotten christmas quilt" that is in the pictures section.
I can't do anything in a straight line without a ruler, so all the straight lines in the borders were with rulers. I also used a wave ruler for the double line in the red borders and then used the wave ruler in the outer blue border as a base for some leaves and berrries that I free motioned.
I have some big circle and arc rulers that I use a lot as well. Those kind of shapes are hard to do evenly free hand.