Neelix and Kim? That would have been atrocious! I still think Bashir and Garak was the best candidate for a same sex pairing. Not that it would necessarily have lasted, but it would have been cool.
I'm glad that Seven/Doctor never happened. I think the characters were great together, but I prefer them as friends rather than lovers.
Odo and Dax though? That's just crazy enough to work! I wouldn't trade it for Odo/Kira, but it's fun in a sort of "what if?" way.