Bitcoin, Ethereum, Moner, Zcash, Grin, BEAM but #VEIL is my choice.
Note that while BTC exists primarily as a store of value and a medium of payment, other coins exist to deliver other value-additives. So, diversity is best as blockchain solutions delve into many, many categories, and different coins have a high potential in their own respective niche.
When it comes to alts, the smart contract chains take up most of the headlines. Ethereum, NEO, EOS, and Tron are fiercely competing to be the chains that enable the smart cities of the future. They may someday face stiff competition from new launches like Zilliqa. Smart contracts offer a solution to wide for just one chain to dominate the entire sector. It's highly unlikely that just one blockchain will take over all smart contract solutions. There's a higher chance that these chains end up differentiating themselves, and this is already visible in the case of Tron, which has quickly become a blockchain for gambling. Meanwhile, EOS may have a lot of gambling applications, but it also hosts some very creative games.
Then you get enterprise blockchains. These entail some form of sidechain solution to stem off private chains for enterprises to maintain the security of their proprietary data. This space isn't that competitive yet but there are some high-flying competitors here like LTO, aergo, and LITION.
Of course, privacy coins are in a league of their own, and it certainly is possible to offer better privacy than the competition. No single coin is there yet but there's a lot of development in this space. Some commenters have already mentioned VEIL, which is an example of a privacy coin that's going through some fast-paced development. While Monero and Dash are leading the way, developments in the Zerocoin Protocol could deliver the best privacy coin to date. Veil's development team is trying to advance the Zerocoin Protocol such that it integrates the best aspects of existing privacy coins. Like Zcoin, VEIL uses Zerocoin Protocol so it leaves no means of traceability. However, unlike Zcoin, VEIL integrates Monero's RingCT technology on its Basecoins, and that allows VEIL to have privacy on both the Zerocoin transactions and the Basecoin transactions.
So, a new project self-funded by the founder of PIVX, which is another privacy coin, is trying to create a new privacy coin. Veil Project (VEIL) uses Zerocoin Protocol but integrates new features that make it more appealing. Veil Labs, the development team behind VEIL, will allow the coin to have multi-block transactions. This means the fixed denomination issue of Zerocoins won't be applicable to VEIL. Also, the Veil Project will integrate Monero's RingCT technology into Basecoins, thereby making Basecoin transactions anonymous too. Given that it uses Zerocoin Protocol, the transaction links would be broken.
By applying RingCT to the Basecoins, all coins within the Veil network will have a privacy feature. So, even if users avoid minting VEIL from Basecoins, they’ll be able to transact anonymously with Basecoins. However, the goal is to ensure minting isn’t seen as a burden. To achieve this, Veil Labs has the ambitious goal of allowing users to make multi-block transactions which address the currency problem of having to mint and then transact Zerocoins in only fixed denominations.
Amazing technological innovations behind Veil are:
Ring Confidential Transactions (RingCT)
X16RT Mining Algo
ANN Tread: https://bitcointalk.org/index.php?topic=5065331
Veil Wallet: https://github.com/Veil-Project/veil/releases
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