BottlePay had it essentially perfected -- tip on Twitter, Reddit, Instagram, Twitch, etc, no-kyc, LN, no fee, etc. For Twitter, their BottlePay bot would see the mention, and perform the "transfer" from the sender's BottlePay wallet to the recipient's BottlePay wallet (with expiration where the funds would go back to sender if the recipient didn't have a BottlePay account and didn't sign up before expiration).

It was beautiful.

And they shut it down. (and have since pivoted into a geo-fenced exchange, with KYC.)

They did a write-up on their new approach: https://bottlepay.com/blog/smashing-payment-barriers/