Nintendogs: Chihuahua & Friends

Nintendogs lets you take care of virtual pets (dogs, obviously) on your Nintendo DS. You can train your puppies by speaking commands into the microphone, pat the pooch with the Stylus, play games like "fetch" with a frisbee, buy toys, food, and accessories, and take part in 3 types of competition to win trophies.

If there are other Nintendo DS users with Nintendogs nearby with both of you in "Bark Mode", you can link the games wirelessly and see your and their dog meeting on both screens.

You initially only have 6 (US/EU), 5 (JP) of the 18 (US/EU), 15 (JP) breeds available when you start playing the game (the six breeds being determined by the version of the game), but as you progress, you unlock more breeds and items to buy. If you connect with another user that has another breed of dog not available to you then their dog's breed will be unlocked for you.