I have come across lots of similar threads in this forum, and have expressed my opinion many times, but I will use this chance again to express (both for me and for forum members) which altcoins I strongly believe in terms of showcasing an exponential growth in 2018:

ETH
LTC
XRP
XMR
NEO
Zcash
Dogecoin
DASH
IOTA

I would limit the list to those coins so far. Some other may join and drop off from the list, we will see.