What are you doing with ripped models?

[Shadowth117]

Well if you wanted to do something quick you could just download the trial for one of the big name ones since they are essentially the full program for 30 days, but if you want something you'll be able to mess with later than you should probably grab Blender. While its got a bit of a learning curve, its undoubtedly the best free 3D software so you'll be able to do a lot with it. There might be other programs that are simpler and good for getting a poor quality (Bad lighting, no specularity or other details) render, but if you want an avatar/sig that looks somewhat nice you are probably going to want to use Blender.

Alternatively, you could get someone here to do something for you if you like. Personally, I don't know how fast I'd be able to do it with school taking up a fair amount of my time at the moment, but I could try and get something together for you if you gave me a general idea or something.

Still, if you're determined to do this yourself it might help to know that .obj files don't have bones and so would require you to rig them in order for you to pose them easily.