The GSD is the only dog with a heavier coat that I find extremely sexy. Otherwise I want to see the muscle tone of the dog. I like when I look at them and think damn he could totally own me as his bitch. The only slight exception is the husky but I'm way picky what ones I find sexy with them.
The sexiest I've actually done anything with and that was only to hold his cock in my hand was a Rhodesian Ridgeback. I want one pretty bad.