It is Monero, and why would you rule it out? We have Zcash and Dash as well, but XMR is our best privacy coin. Privacy coins are mostly old coins so they are usually used for certain purposes rather than an investment as their hype is mostly gone or not too big to make a profit.
Nowadays privacy coins are the target of government so it is very risky when you invest in them. Therefore, you should consider and exercise extreme caution when deciding to invest in privacy coins.