Has to be Spectrecoin (XSPEC) for me. Stealth staking on a trustless set up, min 5% per year and max supply of 21m! The team are doing a brilliant job and recently set up the Spectrecoin foundation in UK

For a mega low marketcap I also like PRiVCY as they have an active dev team and community, max supply of 30million and currently around 50 sats so huge room for growth/explosion