Any shops in China (I believe 99% of them): in wechat, you have "wallet" that generates QR code. Go to any shop, at the counter, show the QR code generated, they have the machine (or wechat app) to scan it. done. Crazy efficient. Most of the people there don't bring wallets anymore.
Most of the restaurants in Shenzhen now has a QR code. You scan it, order what you want, and the food come. Don't need any interaction with the waiter, what I felt a bit inconvenient since I like to ask what's good there.
Starbucks: When I've left home, ordered via the Starbucks "mini-app" inside wechat, when I arrived in starbucks 5 minutes later, it was ready on the counter.
Metro and Bus: get the metro/bus "mini-app" in wechat. you get . In their receipt it is mentioned "blockchain" technology. I'm not too sure if they use it, wondering if they really do use a blockchain behind to generate receipts.
Sending money to ANYONE: never been that easy to send money to anyone. Even if you , show the QR code, and they'll . No more " I don't have cash on me " excuse. There is also no hard limit on how much you can send. I remembered paying all my rent via wechat when I lived there, about 3000 usd every 3 months.