Remember also that with these type of cards it's the atk or def. value before it hits the field. A number of strategies depend on these type of cards besides Zombies.
I've seen a number of outstanding decks that are supported by Giant Rat to bring out nearly every card in their deck. The beat sticks in this type deck are often Enraged Muka Muka and Injection Fairy Lilly. The trample being Gyaku-Gire Panda, and monster removal Exiled Force, Hade Hane, or Nobleman Eater Bug (used of course, in conjunction with Book of Moon) or, if in a pinch, Giant Rat can summon Fiber Jar and be flipped face down with Book of Moon as well.
As well as maintaining field presence cards such as Pyramid Turtle, Giant Rat, and Mystic Tomato can thin the deck, and set up for a kill.