Photoshop by a landslide. Some people use mudbox or zbrush, but that isn't something you'd want to get specifically for toribash texturing. Then again neither is Photoshop...
Just wanted to ask, which is a better program for texturing,
Gimp or Photoshop? Or is there an even better program?
Use gimp! It has multiple options of color programs, and you can make heads or other textures by small pixel! For the final results, zoom out to see your progress, and you should be fine. Welp, that's all. Take it easy.
Matarika|Mobinladen|Youngsandm|Darknis|2WC|Sidtheepic| "Brains are like computers but squishy and very watery :3'' ~D