If you are interested in Toys, I would highly recommended a Papillon. They are extremely intelligent and easily trained. They are also quite athletic/agile for a toy breed. They do well in agility and I've even seen some large Paps in flyball. My pap was never super "yippy" but I have met a few who are. They are in the toy group but are from the spaniel family.
Yes, the Papillon is is a great little dog - my sister had one once and he was the joy of her life. They are loyal, and intelligent, and the right size for somebody looking for a toy, but not a tiny dog. Her dog was not yappy - he barked if someone was coming into the house, but as soon as she "sshhh'd" him, he quited right down. That's not a bad thing, he was protecting his house and his people until he was given the sign it was all okay.
