The best, which is real, and worth it if you have, I think, about 8 mins, is a battle between lion and buffalo with a surprise intervention from the water.
Amazing. More than 25 million views.
And then there are the "fakes" often attached to emails like:
"We had a short vacation in Kenya last October and the safari guide has just sent me this fantastic wildlife video clip of when we saw a cheetah hunting. He even managed to get me in it too. "
This one's another classic
Which must have inspired this one, which is a lot more contrived