I don't know for sure if this is my "masterpiece" yet, but I would say so far it is...
http://www.quiltingboard.com/t-27384-1.htm
I also made a double wedding ring quilt, all pieced and quilted by hand that took me years to make. It was my "masterpiece" for a while, but as I have progressed in my skills, I can see that it is not all that good. I still love it, and it was the first quilt that I made for myself.
I have lots left to learn, and hopefully, I have a few "masterpieces" still in there... :D