Chemistry would seem like a good one, because you fill out so many forms and answer such specific questions, but in my experience, they matched me with entirely inappropriate guys I had NOTHING in common with. Totally random. The free sites - OKCupid, Plenty of Fish, etc. bring some undesirables so I'd have to go with Match for the sheer numbers in their database. Gotta say, I didn't have a lot of luck there either, but will try again soon I am sure.