Pretty unpredictable. Might be a good way to end up with no face like that lady after Travis the Chimp. Also most animals won't give you a pleasant quick death. Great cats will crush your throat and that's one of the quicker ones...but already worse than hanging I think. Something like a bear or a wild boar will kill you slow and painful and honestly a wild boar will probably just maim you.
Yeah, the big cats go for the kill first and are the way to go. India has a fair share of man eating tigers in the wild. Bears eat their prey alive and this has happened to humans. Gators and crocodiles also swallow live prey but a person may get lucky and drown during the death roll. There's lots of deaths in northern Australia and SE Asia from salt water crocs. They're particularly dangerous and I've heard they will learn a persons comings and goings for days before ambushing them.
In the western US, mountain lions are pretty aggressive. Brown and grizzly bears if not hungry, a mother with cubs will probably kill someone coming upon them. I have an ethical problem with putting oneself in harms way of a predator as they are usually tracked down and killed after killing people.
A moose could definitely gorge a person to death. Hippos, rhinos and cape buffalos can easily kill a person.
I would not mess with any kind of primate, they will tear you apart in every way possible.
Komodo Dragons - These are downright scary. Their saliva is toxic so after biting you they will slowly follow you until you collapse and then eat you while you're weak but still alive.
Venomous snakes - Cleopatra supposedly ctb using the bite of an asp. Snake bites are notoriously for being excruciatingly painful though.
Swimming in the Amazon river offers many opportunities to ctb. Anacondas, electric eels, piranhas, parasites, weird insects.