I'm sure I see this thread title every day.
I am not sure what your measure of potential is? Are you looking for the most valuable coin of 2018? The coin that makes the most gains?
I'll let you know what I am watching, and these are all coins that I think are undervalued that I think can go 5x min by the end of 2018.
ONION
Walton
Oyster
I also really like WAVES but haven't ppicked any up yet.