Base

I am building a simple payment service that allows users with a wallet to quickly and easily create and sell digital products via Layers 2s. It doesn't require the user to deploy or interact with smart contracts or approve anything. Completely non-custodial, no private key management (outside of your own wallet)

You just select what you want to buy, add to cart, and scan QR code to connect CB Wallet, Metamask etc. You sign a message that contains details of the website you are on to authenticate, and then accept the token transfer. 
Message signing is basically instant to the user, and the token transfer is completed in 1-2s

I am interested in creating blockchain tools that do not require exposing the user to extra risk and cost via smart contracts. Lots of interesting things can be done purely through message signing and basic onchain transfers. Now that txs on Base and other L2s are so cheap + quick, simple payments are now viable.