As more and more of you are making your final submissions, I'll probably be making fewer and fewer comments. Nonetheless, here's my next set of comments...
@ Clawed Nyasu: I'm really liking your progress on this. Either the shiney on the far left (the black and orange one) or the one on the far right will work fine as your shiney colors.
I think everyone else who has commented on the sprites has helped me figure out what seemed so off about it earlier. I'd say that you ought to try putting a little shading (like a pixel thick or something like that) around the, um, indentations on the drills in order to further remedy your problem with the lack of shading on the drill.
Edit:
Okay, the front sprite is looking a better. It's quite lovely, Clawed Nyasu. I'd say flip a coin between the two shiney color schemes or something since the two are both good.
That back sprite, however, needs some help. Please, please, please, PLEASE redo that arm: it looks like some sort of floppy... thing that was tacked on. That really is the worst offender here and it will be TONS better if you redo it. I personally would recomend changing the positioning of the arm so that it is more similar to your front sprite.