Triangles (this was the most difficult shape):
My Pre-K class had a lot of fun doing this little enrichment activity. After we practiced making the shapes I let them make whatever they wanted to out of the yarn. The students were quiet creative and it was fun to see them choose to make things like: their first letter of their name, a shape that we didn't try as a class, a princess crown, etc.
What kinds of hands on activities are you doing with shapes right now?