Wow, so many things come to mind. "Mine" is by far my favorite. "I love you", is always a good one. There is one thing He says to me that always makes me quiver, He says in French. It's impossible for me to keep my lips off of Him when He utters it.

As for my favorites to say to Him... I'd have to say it's a tie between "Yes, Love" and "I love you".