Well, Komodo dragons DO eat water buffalo. They have "toxic saliva" so when they bite the buffalo (which is MUCH bigger than them), the poison enters the wound and, eventually, kills the buffalo. Even though the buffalo is about five times larger than the Komodo dragon. Quite amazing, really. ^^
EDIT:
Very true, Drago. The ones I would like are as followed:
Eagles vs Rabbits
Bear vs Deer
Polar Bear vs Seal
Snake vs Frog
Lion vs Elephant
Wolf vs Deer
Komodo Dragon vs Water Buffalo
What do you guys think? *puppy face*
Those all sound great, except for the Lion vs. Elephant, which isn't very realistic. Lions and predators in general tend to leave adult elephants alone, but lions will kill an elephant calf if they get the chance. So maybe that could be changed to 'Lion vs. Elephant Calf'.
That's true...but then again it IS possible. So maybe as you progress you could get bigger and bigger (as an elephant), until you're nearly impossible to hunt. Sort of like the Shark vs Cape Fur Seal, except in that one you get faster and faster (seal) and stronger and stronger (shark).
DOUBLE EDIT: Oh, and maybe you can keep growing your pride (lions) or herd (elephants) as more members or NPCs come. Then, as a lion, if your pride is big enough, you could take down an adult elephant ;3