I have a list of WHAT NOT TO BUILD.
I won't build anything that has been over-modeled or offered as a kit or an ARF. I don't want people thinking I just glued a kit together, or the other, and far worse possibility.
I will not build (another) retractable-gear model unless I actually use retracts. They punish you too much on flying points.
I will not build a Shoestring, Little Tony, or any model that has been used as an RC pylon racer. I certainly don't want my plane to be mistaken as one of them.
On a note of political correctness, I chose to model aircraft only from the United States of America, NATO, and the FWMAF. A lot of people, other than dedicated scale modelers, will assume that my choice of subject matter indicates support of the chosen power, and maybe rightly so.
The above list tends to exclude a lot of designs, but there are still a lot more left than anybody has time to build.