Nintendogs

This is one of those games that makes you want to buy the Nintendo DS.

According to an article in Wikipedia,

"The game has been well received by critics, and in the May 2005 edition of the notoriously unforgiving Famitsu magazine, Nintendogs received a perfect 40/40 score. Only four other games have attained this score"

And yes, they have a King Charles Cavalier version.