Besides Gold?
Silver. To be specific generic pre-1964 US coins. Dimes are probably your best bet. Gold, even in the smallest coin available has tremendous value. Small silver coins would allow you to evade any seizures, transaction controls or price caps. They are familiar to people and value is easily determined as a ration of face value, currently around 12:1. Not to mention that gold isn't really used for anything except trading on exchanges while silver is in heavy use as a industrial metal and usage currently exceeds supply. Get them by the roll on eBay. Sometimes, if you play it right you can buy them at melt and then get cashback from Bing.