So you have started a new game using the Third Person Template? Awesome! If you are looking for guidance on how to do specific things or perhaps just looking at the blank canvas of endless possibilities, this doc contains ideas for things you can implement.
Read up and watch some video on the Blueprints Visual Scripting system. Sometimes it is not about what to do, but how you can do it, and knowing more about Blueprints will enable you to rapidly prototype ideas, even if you will ultimately be working in C++.
Create a HUD for your Third Person Game using Unreal Motion Graphics.
Why not add some Destructible Meshes to the environment? Check out the Destructible Actor Documentation and the Blueprint Communication Project for methods on how to do this!
You can add AI Characters using Behavior Trees to your game and have them chase, flee, help, or harm the player.
If you end up killing your Player, maybe you will want to be able to respawn them? Check out this how to guide for Respawning the Player.
The default character is kind of bland, create your own or get a new one from the Marketplace located in the Epic Games Launcher.
Using what you learn in the Blueprint Communication Project tutorial, add some environmental hazards. Exploding barrels are the "gold standard" in games, but there is a number of hazards in the world to recreate in your game:
Large fans! They can also push or pull the player/AI.
Toxic fumes! Make them expand or move around.
Lava! Because LAVA! Ok, really because it is an effective area denial hazard.
Slippery surfaces, like ice. You can modify the friction of a surface so the player will slide on them!
Alter your ThridPersonCharacter's jump height, run speed, mass, or a number of other properties on its Character Movement Component to create unique-feeling gameplay.
Launch Pads are common in a number of game types, including first person games.
Check out the Unreal Engine Forums for even more hints, tutorials, guides, and ideas!