Hidden gesture to scroll to top of SMS list, or glitch? I've noticed that sometimes my phone (Samsung Galaxy S3, Android 4.3) jumps to the top of a SMS list. This is a useful feature that I'd like to reproduce but I never found a gesture or option for that.

According to these answers, there is no predefined gesture on Android and the solution is to install an app on a rooted device. However, a couple of times it worked as such by tapping twice on the top edge of the phone; I don't know if it's an undocumented feature and is supposed to work this way, or it's a glitch.
If you're running the stock version of Android 4.3 on your S3, this is actually a feature provided by Samsung's TouchWiz. You can find the toggle for it in Settings &gt; System &gt; Motion. You can find documentation for it on Samsung's support section. It says:

Double tap to top: When viewing a long list, like your contacts list, or scrolling through a website, tap the top of your device twice to be taken back to the top of the list or page.