Sometimes I used to let my dog lick my penis when I was younger.
http://captionsearch.com/pix/urvzh7oyn.png
His tongue felt so warm, it was a bit much for my penis and balls. I was afraid he might get confused and bite a little at my penis or hair or something not realising how sensitive those parts are, I doubt it but you don't want to take chances.
I preferred when he licked my feel. He would lick my face as well, even if I tried to push him off it, but I nearly always hated that because I've seen where else he'd been licking sometimes....