There are several ALTcoins that are backed gold. For example: DigixGlobal, AurumCoin, OneGram.
In addition to these there are several altcoins pegged to USD. Tether (Centralized), MakerDAO, TrueUSD, BitUSD. There is a cryptocurrency pegged to mining energy (stablecoin with limitations on maximum processing power) but I cannot remember the name. Rare Pepe assets have been minted as physical cards. Precious coins with BTC/LTC/DOGE encrypted within. Perhaps more but that's what I am aware of personally.