Extreme Low Poly Models are needed for mobile games since most devices lack a GPU (3D accelerator). These proof of concept models include full skeletal animation with bone attachments, averaging about 140 polys (tris) per base character.
The helmets, backpacks and weapons are separate objects, and attached or removed from the bones via script.
Depending on the viewdistance from the camera, these models can often be reduced to as low as 110 polys. The human mesh shown here is about 140 poly.
These are actual screenshots from a couple 'proof of concept' mobile games.