It's hard to choose only one fav muscle group, but I would have to go with legs. Favourite body part overall is the eyes. I love eyes, I always notice them first before anything else. You can see a persons soul, how they are feeling etc through the eyes. They never lie.
i agree, well not actually the eyes itself, but the way a person uses them, facial expression. you can decipher 90% of a person looking into her eyes, its incredible. The other way is true as well. More then once when a chick looked right into my eyes I felt like she was looking inside me, kinda of discovering all my secrets in a matter of miliseconds, pretty strange once I kinda of felt naked in front of that woman with really keen eyes. I know when Im with the right woman in front of me when its just one look and she is already making me shy.