What are the most promising low market cap coins that are still under $1?
Don't invest in Deep Onion or NXT, if you want to make money then invest in a coin with a high daily volume so you can actually cash your money out when you make the money.
Deep Onion does have a decent trade volumen in Cryptopia at least. It is highly liquid and it is going to be a great hit in 2018. I think that we have not yet realised how important anonymity is for cryptos.