Based on the math by Kokichi Sugihara, I've made my own variant of the right-pointing-arrow. When rotating, it still points to the right, and in the mirror it always points to the left!
Comes included both with and without a support that makes it possible to rotate.
Compared to other arrows on here, this one is designed perfectly using math, and the shape is curved (not sharp) to make it less obvious in real light conditions what's happening. Best viewed at 45 degrees angle.
My other illusions: https://www.thingiverse.com/Matsemann/collections/matsemanns-ambiguous-cylinders
The code & stuff: https://github.com/Matsemann/impossible-objects
The top needs to be perfectly smooth, so use high resolution. A tip is to enable "Use adaptive layers", so that the top can be printed high res, but the body a bit faster and less detailed.