Ever type out a message, hit send and immediately regret it? OS X Daily points out that if you're quick enough, you can enable Aeroplane Mode to cancel that message from being sent.
As long as the "Sending..." message is still displayed at the top of Messages, you can drop into Flight Mode (pull up on the Control Center and tap the aeroplane icon) to cancel the message (this should work fine on Android too). If you catch it in time, you'll get a "Not Delivered" note. Because of the message size, this works best with multimedia messages, but if you're quick you can catch texts too.
How to Cancel Sending a Message or SMS from iPhone [OS X Daily]