ETH and DASh on which I have a great trust. Hope it will grow with the pace more than 5X in 2018
I will also go for ETH as it is still the number one altcoin. There are many reasons for it and one reason being it has smart contract which produces lot of smart tokens which people are heavily investing on in the form of ICO.
I am not sure about Dash but i will say Ripple can be the 2nd best coin in 2018.