Bitaddress.org: an open-source, client-side tool for creating Bitcoin paper wallets.

Walletgenerator.net: another open-source, client-side tool that supports multiple cryptocurrencies, including Bitcoin, Litecoin, and Dogecoin.

MyEtherWallet: a popular tool for creating Ethereum paper wallets. It also supports other Ethereum-based tokens.

Liteaddress.org: an open-source, client-side tool for creating Litecoin paper wallets.