I would say maybe a cat, specifically a linx or something because of the fluidity of felines. Not a cliche tiger or lion though.
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On a somewhat related note, i believe it's a mongoose or marmaset that kills and eats snakes. So they're pretty badass. If you've ever seen one move...not unlike RA style

Mongoose are sleazy little bastards, but they remind me too much of rodents (which they are not obviously). Marmosetts are cool i guess. Cats are too cute-ish for the sigil. I still stand with the fox, both in their stereotype and by the way they look - awesome. Snakes are alright too, so i'll make one with that and we can compare. Also, it doesn't necessarily have to be an animal, i only picked one because it was easy ;). I avoided commonly used cliches like tigers, bears, lions etc, fox isn't so commonly used with the exception of mozilla, so i thought that was a good idea.