Sure, I already have hundreds of photos from flickr of dogs chewing on stuff. The problem is not the dog as much as the finger. What does a chewed finger look like, and what does it look like rolling around in dog saliva? I suppose the reason you don't see that in a lot of movies is that it's a difficult effect to do in any interesting way.

Heh, I'm sorry. I didn't realize there was some rivalry going on here. I suppose I broke the golden Internet rule "never post in a forum you haven't lurked for a couple of months".