Anything by Skynet3020 in Poser format is awesome.
http://www.renderosity.com/mod/bcs/vendor/skynet3020

The .OBJ models are good as well but the Poser format models have moving parts.

Also this by T. Newton is great. Better still, it's free.
http://www.sharecg.com/v/70075/browse/11/Poser/CRUCERO-SPACE-ARMY