Well, I have a huge crush on a really shy/quiet/nice boy, and I'm rather more outgoing.
But I don't like him because I like that "type," I just do... soo... I guess I'd have to say about a 5 or something? If I want to be in a relationship with somebody like that, though, they need to man up at least a little bit and ask me out. Hopefully they'd get over their shyness if we were together, otherwise it just wouldn't work.
That's in a more romantic sense... as friends, I love talking to them. I'm probably more likely to go over and sit down next to a slightly shy, quieter guy who's alone than some cocky dude in a big crowd. So in a friendly sense, I'd say maybe an 8. That type of boy usually makes a good friend once you start it.