1.Monero (XMR)
Its completely untraceable and gives owners the power to have complete control over their data and their anonymity.
2.Navcoin (NAV)
Built on Bitcoin Core, its a low fee cryptocurrency with added features and upgrades. Many investors have Navcoin on their list of the best privacy coins of 2018
3. ZCash (ZEC)
ZCash isnt that popular yet in comparison to other privacy coins like Monero or Navcoin that means theres more growth opportunities for investors.
4.Verge (XVG)
Verge has open-source software so followers of Verge can input into future decisions and developments of the technology.
5. PIVX (PIVX)
It has a strong following and community with fans even creating art and advertising around the Pivx brand.
6. Spectrecoin (XSPEC)
Most privacy coins already have a huge market but Spectrecoin arent in the same league meaning huge potential for cryptocurrency investors.
7. Sumokoin (SUMO)
Its a hard fork from Monero one of the most popular privacy coins on the crypto market right now.
I've been always fan of Monero/Dash but I just think they are so overpriced now. I think upcoming coins like DeepOnion, Spectrecoin have much better potential like you say especially for investors. However if you look at the features of DeepOnion for example you will see that their tech/roadmap is also superior to them.
2018/2019 will be the year of privacy coins.