It's probably way overkill but sometimes I get a wild hair to do something specific. I've converted the model to high res, smoothed it, added surface details and dents, and probably tomorrow will get some time to give it materials and bump maps, bake the texture and apply it to the low res model. If not tomorrow, hopefully before the weekend. Work's a beeyatch right now.
Edit: I get asked about what stuff I use all the time, so just to cover that, so far it's: 3DSMax, Maya (sometimes I import between them, they both do different things better), Crazybump, Zbrush, Photoshop.