UE4 Animated Static Mesh

Absolutely no bones, skinning, or morph targets.
Vertex Animated Static Mesh. Can be used as an impostor for NPCs, instanced for RTS games, and several more options.

You can bake in several animations and skip through them, or swap to another version of an animated mesh, skipping the transitions.

[vladtheclad]

Good side: cheaper than Skeletal Mesh.
Bad side: not customizible, too expensive in memory stamp - every vertex baked.

[cobalfrostwyrm]

Useful for instanced crowds, bad for pretty much everything else.

[bbc]

it's hard to do animation blending

[Thunder_Owl]

Very good. I kinda hate skeletal meshes.