Technically not a coin but since others have posted exo here's some bullion. Although these you can't buy anwhere close to spot.
Valerian I of Alexandreia Troas AE20; Alexandreia Troas Obv.: IMP LIC VARERIANVS AV; laureate, draped, cuirassed bust r. Rev.: COL AVG; grazing horse r. // TROA Reference: SNG von Aulock 7573 var (ending of both legends)
Nezak Huns, Spalapati Deva AR Jital, AD 750-850 Obv.: Horseman right holding lance. Rev.: Bull left, Sarada script. Reference: Tye 5.
Kings of Macedon, Philip II (359-336 BC) AE16, 5.7g, 12h Obv.: Head of Apollo right, wearing tainia. Rev.: ΦΙΛΙΠΠΟΥ; youth on horseback left, N below. Kings of Macedon, Philip II (359-336 BC) AE17, 6.7g, 12h Obv.: Head of Apollo left, wearing tainia. Rev.: ΦΙΛΙΠΠΟΥ; youth on horseback right, S below.