Meshes bound to a hierarchical skeleton of bones which can be animated for the purpose of deforming the mesh.
Static geometry which can be cached in video memory and rendered by the graphics card.
Image assets used in Materials to apply to surfaces or drawn on-screen by the HUD.
The NVIDIA APEX Physics Lab APX and APB files.
Using IES Light Profiles in Unreal Engine 4.
The basic requirements for getting sound files into Unreal Engine 4.