What? No Duck Hunt? What a joke. Here's my superior list:
1) d (it can smell things out for you, eat rotting corpses that you can't stomach, you can teach it to steal, or you can eat it in front of a little girl to make her cry, and if you piss it off it will kill you)
2) the dog from Duck Hunt
3) Rush from Mega Man
4) KK Slider from Animal Crossing (he has more soul than most game composers)
5) Amaterasu from Okami (the god of all creation, the sun god, in dog form)
6) zombie dogs from Resident Evil
7) Dog from Shadowrun (his name is Dog, he controls your destiny, he teaches you magic)
8) Interceptor the badass ninja dog from Final Fantasy 6
9) Poochy from Yoshi's Island (you ride him through an ocean of lava, he is invincible)
10) Parappa the Rappa
(Sorry, I never got around to finishing Half-Life 2 before some jackass stole my PC. I still have the install disc for some day... when my dreams come true.)