Crocodiles. Even when someone tries to make them look funny, as in the Disney version of Peter Pan, they still come off as menacing. Nothing looks more like a carnivorous dinosaur than a crocodile. Then there's their demeanor: they just lie around literally like logs, soaking up the sun, until they're ready to assassinate something. Sharks get all the bad press, but on three continents crocodiles kill people every year: Asia, Africa, and that no-so-safe-as-the-tourism-authority-would-like-you-to-believe land, Australia.
No wonder they live a long a time. Except for eating and reproducing, all they do is eat and swim. Sounds like some ex-neighbors of ours.
Humans are such visual creatures. Take away big eyes (baby seals) and fur (most mammals) and often what is left is the ick factor.
Not many creatures have a bigger ick factor than the spider. It seems like the more legs an animal has, the more alien it appears to humans. In that regard the centipede and the millipede have spiders beat. But spiders also have multiple eyes, and poison fangs: the words "poison" and "fangs" being enough to send any creature to the top of most folks' ick list.
Inhabitants of the U.S. and Western Europe have enough issues dealing with spiders of modest size. Those of us who dwell in the American Southwest can speak of silk-spinners boasting considerably more impressive dimensions. You have to go to the tropics of the world, though, to find the size champions of the spider world. Spiders whose legspan easily exceeds that of your open, spread palm. In contrast to the majority of popular feelings they regretfully inspire, these rainforest denizens are often startlingly beautiful.
There are river otters, and clawless otters, and sea otters, and then there is the giant otter of South America. Six feet long and up to eighty pounds in weight, it is a denizen of the rainforest that is nobody's pool pet. I hold immense respect for any creature whose principal diet is piranha, and who munches solid bone with as much gusto as flesh. Once nearly hunted to extinction for their pelts, giant otters are making a limited but measureable comeback throughout their range, even returning to rivers from which they were originally exterminated.
Cross a seal with a river otter, brush on some canine features, and you have the giant otter. The result is every bit as cute and cuddly-looking as your average otter. It's just important to remember that this kind is the only one that is entirely capable of treating your forearm the way you would a fried chicken drumstick.
So iconic and blatant is the tiger in its coloring, that to observe one close-up and in the wild is like seeing a cartoon come to life. There's a slight disconnect in the brain, as if this enormous mass of brightly striped orange sinew and muscle and bone has been dropped into the real world from some other reality. Real cats don't look like tigers. They're more subdued in hue, more shaded into their surroundings.
It's only when the tiger moves, when it gets up and walks around, or yawns to display teeth like daggers, that it fully impresses its reality on you, and you're grateful for however much distance exists between the two of you. Because no matter how somnolent and lazy it appears, the quiet, brooding cat is the pawed equivalent of a Remotely Operated Device fully capable at any moment of blowing up in your face. Or taking it off.
It's a funny thing about great white sharks (and that's not a contradiction in terms). They smile. Exactly the kind of smile you would expect to get if you crossed the Cheshire Cat with Dracula. Coming straight at you, the expression is downright unnerving. Here's this one-ton plus eating machine, the top Piscean predator in the sea, with a mouth big enough to swallow you whole and teeth serrated like steak knives, and it's grinning at you as it makes its approach. A frozen grin, to be sure, but one as unmistakable as that of any porpoise.
Then it opens its mouth, and the grin goes away, to be replaced by a black gullet as dark and profound as the entrance to the River Styx. Which, if you are not suitably aware and guarded, it very well might become.