One of my personal favorites (the one i have now) is the Scorpion and the Wasp but I cant remember which animal is the father and the other the mother. There isnt really a best breed it just depends on how you play the game. When you start off DO NOT attack any animals until you get your damage up. Id wait until your level is at like 10 to 20. It also depends on which powers you have. The best one is giant (then again i dont have all of them unlocked). If you do want the giant you can wait until you update one of your stats by six to get a new powet or you can combine two animals. I think one combination to get you the giant power is gorilla and alligator although im not sure. Bigger animals (gorilla, elephant, bear) have a better chance of getting the giant power. I personally use giant and heal. Update your damage first then when you feel comfortable update your health, running speed, accuracy, etc.