The well-known altcoin investments are:-

Cardano: This is a blockchain platform that offers faster transactions and lower fees compared to other cryptocurrencies. 

Polkadot: Another great investment option is Polkadot, a blockchain network that enables various blockchains to work together. 

Chainlink: Chainlink is a decentralized oracle network that connects smart contracts to external data sources. 

Uniswap: Uniswap is a decentralized exchange built on the Ethereum blockchain. 

Binance Coin: Binance Coin is the cryptocurrency of the popular Binance exchange. 

Polygon: Polygon is a layer 2 scaling solution for Ethereum that offers faster and cheaper transactions.