It's not really hidden but amazingly undervalued still...its STELLAR XLM!!! This is going to be huge in 2018.
Recent news of collaboration with IBM is just the start. It has real world use case and there is serious momentum gathering behind the scenes here.
Of course, do your research and follow it closely. It has had a few small pumps recently but for 2018 I think this one is a no-brainer (as much as there can be a no-brainer in crypto!!! Haha)

I have switched my altfolio to 90% XLM now