My biggest bet is on privacy coins. There are some out there like Verge, SUMO but especially XSPEC. I have bought some of these coins but i think XSPEC will grow a lot in 2018. There are a couple of reasons for it, the price is too low at the moment compared to what it offers.
For example, it has TOR integrated in the client and you can use stealth addresses. Soon version 1.4 will be released and a new website as well, this will give XSPEC a boost. So, it has a bright future ahead of it.
Wow, finally somebody who also mentions Xspec. Pretty much the best privacy coin out there. Still relatively low on the radar and low marketcap so much room for growth. Once 1.4 is out and marketing will start become more priority, further growth is likely. My best bet for 2018!