Alright, so this guy was sitting around unfinished, and I saw the contest, and so here he is. Fully rigged, fully textured (morguefile.com, checked the licencing), and he's even got a walk and run cycle sitting in the action editor.
NOTE: I am submitting this blend for the contest, if you'll let me. I know it's not really a traditional mech, but I think he should be able to qualify. If not, it's cool.
OTHER NOTE: This is not finished. I just wanted to post this to see if I can use it in the contest. I'd like to post an update with a better rig, bone shapes, and more detailed textures.