However, with great features comes great confusion, and not all the settings are immediately obvious.
Individual read receipts
This should have been a thing a long time ago, but iOS 10 finally adds the ability to selectively choose who gets read receipts. This is a good thing, because read receipts are mostly awful, but occasionally useful. Nobody wants the majority of people knowing that they are blowing them off and ignoring messages (or, for that matter, getting worried because it took them more than 0.0002 seconds to reply). But for a few select people, it's good that they know that the person they are calling has read the message, so they can stop calling again.
Several posts already discussed Momento, which is easily the best standalone Message app so far. It takes several similar images (like the three failed group photos taken before) and turns them into one perfect animated GIF that the user can spam to people.
The results are occasionally useful, and always hilarious. Yes, it's a good way to relive some great experiences, but mostly it's a reminder that computer vision software still has a long way to come.
Apart from the silly GIF apps, Messages also has a lot of silly sticker apps in the store. When somebody rounds up the most useful Messages apps so far, it will not be surprising to see the Super Mario sticker pack making it into the top 10.
Phil Schiller spent a lot of time on stage in May explaining how Messages in iOS 10 gives users all sorts of ways to make their point. Users can send their message big, small, secretly, with confetti, with ballons, or basically however they want.
In case somebody did not have enough ways already to send their message, Apple imported the Digital Touch feature from the Apple Watch. It gives users better options to draw their own symbol, or they can press and hold for different options like sending a heart or a kiss.
If a picture is worth a thousand words, a map of your location must be worth an entire novel. It's easy to use the Messaging app to send a location to a contact, either on a constant or one-time basis.