The star of the Halo games is, of course, the Master-Chief. Kidnapped as a child and subjected to morally-dubious training and experimentation, Chief (also known as John-117) became the leader of the SPARTAN II unit of cybernetically-enhanced supersoldiers. This unit logo was given to them by their 'mother', Dr Catherine Halsey, who gave John a coin bearing this logo when she first met him. It eventually appeared on their equipment and on their MJOLNIR armour's HUD to desinate another member of the SPARTAN II unit.
Since I seemed to be on a bit of a Halo binge I decided this was one I had to do (and now I have to do another one, as I've now got three and odd numbers are the work of Satan). Again it can be used as a coaster or for home decor, gear decoration or as a cosplay badge or emblem. It does, of course, have the usual 3mm x 5mm holes for neodymium magnets.
If you'd rather I did the work for you instead you can buy one, printed and assembled, in my Etsy store - www.etsy.com/uk/shop/enterprisexddesign