Here's my take on the IDIC (Infinite Diversity in Infinite Combinations) pendant worn by Spock on Star Trek. Here's what Memory Alpha has to say about it: https://memory-alpha.fandom.com/wiki/IDIC
I made this as similar to the on-screen images as possible, but it is a completely original design that I created with OpenSCAD. The design is suitable for use as a pendant, pin (held in place by a magnet), or refrigerator magnet. It is unclear if commercially selling prints of my design would be seen as violating rights claimed by Gene Roddenberry as inventor of the IDIC, so I advise against doing that; the design is posted here for personal use only.
The design has a few spans, but nothing critical. The big span is in the opening for the 20mm diameter, 4mm tall, "magnetic button with foam adhesive" -- which will be hidden by the magnet stuck to it, so it isn't critical. I printed this relatively slowly, around 60mm/s, to get the smoothest possible surface finish on the Silver PLA. A better finish could be obtained using metalic paints, but this is literally as it came off the printer.
There are three things you need beside the printed part given here:
A diamond-like gem of 10mm diameter. Obviously not a real diamond, but is should look somewhat like one. The one here is https://www.thingiverse.com/thing:379105 scaled to 10mm diameter and printed 100% filled in clear PLA. A cheap plastic one from a crafts store would be significantly better. In either case, the jewel can either be welded or glued into place; I welded this one in using a soldering iron.
A magnetic button with foam adhesive. This 20mm diameter magnet is used to hold the part as a pin or refrigerator magnet, and is not needed if the part is used only as a pendant.
A cord for the pendant. Here, I used some simple string, but any cord or chain-like material will work as long as you can feed it through the 2.5mm channels printed into the part. The ends of the channels provide an opening making it easy to fix the cord; here, I simply tied a knot. Obviously, it doesn't need a cord if used with the magnet.
Although the pendant has some height, the part that is thickest does not need any fill, so the center of mass is still close to the back. This helps the pendant hang nicely. Note that it deliberately hangs at an angle, approximately matching how Spock's was worn.