I think everyone has seen the classic ANS or utility created postcard with a small simulated fuel pellet attached. My local utility even passes out 3d printed fuel pellets (in rainbow filament!) at Pride every year. But these two are a little bit nicer than average. The Trojan pellet is the nicest conventional pellet display I've seen, which cool graphics embedded in a reasonably sized lucite paperweight.

But the absolute king is my newest arrival. Westinghouse made a small number of these to demonstrate what fuel elements for the NERVA rocket engine would look like. I don't know if they're plain graphite, but in any case a neat bit of nuclear history