Domino Rally

Domino shapes similar to those manufactured/distributed by IDEAL and Goliath in the UK as part of various 'Domino Rally' sets.

A plain/symmetrical domino (not sure why you'd ever use this unless it was to print out more interesting colours) - Print this standing up.

A hinged domino (could be used to replace those on the various fixed-tracks) - print laying down. Untested - Print this laying down.

A weighted, hinged domino intended for use in the loop-de-loop (such as in Goliath 81007 "Domino Express Amazing Looping"). The current model is too light to reliably trigger the loop as I believe it's purely plastic, whereas the one from my childhood had a block of what looked like lead in it for the top-half of the domino.
This compromises and includes a hole for an M4 nut (may need glueing depending on tolerances). This works well - better than the original - Print this laying down.