I'm developing a small 3D game for the android and I'm trying to keep the poly count as low as possible. My question is: Is it possible to rig and skin a model with the symmetry modifier. e.i: Will I be able be able to rig, skin and, seperately, animate the side of the model created by the symmetry modifier or do I have to collapse the modifier beforehand?
Once you're finished modelling your low-poly mesh, collapse the symmetry into the mesh so you have actual geometry instead of just half geometry and half "virtual geometry" (which would not be able to get rigged).
If your concern is about 'vertex assignments' an 'weighting', the Skin modifier has tools for mirroring the skinning you just did on half a mesh so you don't have to repeat the same for the other side and waste time. This way, you can skin half of your mesh (assign vertices to bones, weight the vertices etc.) and use the mirroring tool to "paste" all this work to the other half of the mesh for each symmetrically-relative vertex.
This is all done under the Skin modifier, so at first you really need to collapse the symmetry and finish the mesh before proceeding to this.