Cool hidden UE4 tools?

I’ve recently found out about the GameplayAbility (Wiki) system within the engine, and was surprised such a powerful system was hidden and not heard of too often (and unsupported). Other examples of very useful tools have been custom movement modes and the extensive moddability of the AIPerceptionComponent. Of course, there’s not much to be found on these unless you really go digging.

What’s some other useful stuff that could be easily overlooked?

Ctrl+numbers locks a viewport to where you are looking
Press numbers to snap to the view

You can set the speed of WASD in the editor with the scroll wheel. Very useful.