I'm in the middle of an EDF project and a robotic arm project, so I'll share what I've been printing.

• Something that attaches to mini servos securely.
• Sections for a robotic arm that make use of mini servos as joints.
• Something that secures a 68mm EDF down, so that it can be tested from a distance.

If none of these strike your fancy (Why ever would they not, seeing as they are so universal in application and not at all specific to me? _/s), try designing and 3d printing a (nice)* mobius strip or a klein bottle. No internet cad files allowed (no thingiverse, etc). It's probably going to be hard, but I've seen people do it in Fusion 360. I haven't tried yet.

*(By nice, I mean there shouldn't be sharp turns, or even abrupt changes. The thing should be fairly smooth.)

Or, make a better printing press model than I did. This was modeled in an hour or two, but someone else printed it, so ignore the yellow-blue color scheme.