As I have said several times in this site. Jacob's Ladder. I still have it down stairs waiting for me to take the quilting out of it. I did it in White and Navy. I would be chain piecing and then find out that I the wrong piece on top and have to tear them all apart.
I wasn't happy with the Log Cabin I made either.
Other than that I really haven't disliked any of the patterns I have made. Paper Piecing would be my all time favourite. Followed One Block Wonder/Stack and Wack.