I know I konw, it's going to be a very long reply to you OP and I'll sound like a big shill :P But I am extremely passionate about a project and think it is an absolute underdog both in terms of its recognition but also from a purely speculative angle. It's 100% undervalued and under-appreciated, and let me explain exactly why. Because it's a very long post and I don't want to really waste your time, I've put important parts of the post in bold so you can glance quickly at the post :)

So for me, that project is: Particl (CMC rank: 238 at the time I'm writing this -> huge organic and also speculative upward potential)

tl;dr
The Particl projects has excellent coin economics (investment value) and has a shot at actually getting mainstream traction.

Non-tl;dr
Why is it an underdog? Everything about Particl is designed to dramatically lock the PART supply out of circulation. It's value is going to organically rise as the platform gets traffic. I also not only believe the coin's economics are among the best in crypto, but I also believe the project actually has a shot at getting mainstream traction (unlike most projects unfortunately...imo). I'll explain why of course...stay with me :)
What is Particl? It's a privacy-focused decentralized application platform designed to work with almost any coin. Dapps are accessible directly from Particl's main wallet in the same way you would access an app on your mobile phone: Particl's wallet is kind of like an OS (i.e. Android or iOS) and each Particl Dapp is like an application from within that figurative OS.
Particl's first Dapp: A private-by-default (as in...anonymous) and decentralized marketplace (eBay-like, in a way). It charges vendors no fee (except for a small listing fee as anti-spam measure, but no final value, subscription, yearly, or anything other kinds of fee) and uses RingCT to make all marketplace transactions untraceable by default.
Why do I say it's an underdog?
I say it's an underdog because its coin has enormous growth potential. This is due to the fact that everything within the Particl platform is designed to reduce its available supply while its demand is designed to be constantly increasing:
1. Its first Dapp (the marketplace) uses an escrow system that doesn't require any third-party and is based on double deposits and smart-contract (MAD game theory). In short, both the buyer and vendor need to make a security deposit that only gets refunded at the end of each transaction. That means everytime there's a marketplace transaction, the value of the purchased order + two equal security deposits are locked in escrow for a certain duration (until both parties confirm the deal as finalized). In other words, the more activity the marketplace gets, the greater the number of PART coins taken out of circulation and temporarily locked in escrow (see this tweet that shows the numbers).
2. There is passive income potential for users (PoS with cold staking). Currently, the interest rate is 4% a year, and it decreases 1% every year until it stabilizes at 2% forever.
3. All the revenues generated by the platform are entirely redistributed to the stakers. For example, its marketplace (the first of many future Dapps) charges vendors with a very small listing fee, which is then redistributed to stakers. While that fee is small, it does add up as more products get listed simultaneously. This "platform revenue" is entirely redistributed to stakers which means passive income becomes more profitable the more activity there is on the platform.
4. As staking becomes more profitable, more people will want to keep their coins on their wallet to benefit from the platform's passive income. This might reduce the available supply in the markets.
5. The marketplace will eventually accept almost all coins, but any non-PART marketplace transaction is automatically converted to PART in the background (without the user needing to worry). This is because the marketplace has to use the PART coin for its smart-contract escrow and to use the RingCT protocol to make transactions untraceable. In other words, any marketplace transaction adds to the demand for the PART coin, even if a purchase is made in BTC, ETH, or other coins.
6. There is no token on the Particl platform. All future Dapps will only ever use the PART coin as the underlying currency, even though it may accept other coins to (remember, non-PART transactions do end up as PART transactions in the background). This means that as more DApps go live, the demand for the PART coin will increase exponentially.
Will the marketplace even be used?
Yes! Well...In my opinion, yes! ;)
1. The big problem with crypto right now is that it is hard, geeky, and ugly. At least...for 99% of the people shopping online. The Particl team is building its project with the "mainstream" audience in mind: the marketplace is going to be super sexy, easy-to-use, with the lowest possible barrier to entry. Particl is building its platform, and specifically, its marketplace, to be as easy to use as any other marketplace online (i.e. eBay). While you will initially need to download the wallet, there is a web interface planned and the team is even looking into eventually add fiat gateways. For the moment though, users will be able to use Mubiz, a company building a user-friendly interface for the Particl marketplace. Mubiz will make possible paying anything on Particl with traditional means of payments (i.e. banking cards, paypal, crypto, etc) and will take care of all the geeky stuff on behalf of customers (i.e. security deposits on escrow, customer service, returns, shipping, etc), and it will be as easy to use as any other marketplace.
2. Vendors will pay a ton fewer fees. Amazon can charge up to 45% per sale, eBay charges around 10% on average without taking into account the payment processing fees. Alibaba generally requires a $25,000 security deposit + $10,000 yearly subscription fee on top of other fees. Particl Marketplace will charge vendors only a few cents per listing. Vendors will have more profit per sale, more money in their pockets by using Particl. I don't expect them to drop other marketplaces, but redirecting their returning customers to the most profitable option is always something vendors tend to do.
3. Customers will gain access to cheaper products. Since vendors can save so many fees, they can reduce their prices to gain an advantage over their competitors. If they can save, for example, 20%, well they might want to lower their prices 10%, get more sales volume and still make more profit per sale. The customer pays less, the vendor earns more.
4. You don't even need to buy PART to use the marketplace. You can use BTC, ETH, IOTA or whatever is your favorite coin. Don't like crypto, then create an account on Mubiz and buy something off Particl using Paypal.
Particl is a platform solving real-life issues (marketplace fees and privacy) and designed to have its available coin supply constantly reduce but also have its demand constantly increase. This will lead to a value increase until it finds its true value based on the activity volume it gets.
The project is also designed by a skilled team (their Github is one of the most active in crypto with quality contributions) that understands that in order to gain mainstream users, your product needs to be super intuitive and easy to use. Most crypto stuff will be in the background and the barrier to entry will only get lower as the project progresses.