I always thought salamanders and newts (for what difference there is between the two) looked cute as hell, especially fire salamanders, as to certain toads in the genus Atelopus, and TTX is also found in at least the eggs of one of the horseshoe crabs, Carcinoscorpius (monotypic genus), and to a degree seemingly the entire crab is toxic although it has been eaten, and as far as sealife goes its quite common, some polychaete worms of the nemertelline variety pack a heck of a punch in terms of body content of TTX and derivatives, and some use it as a venom, with an eversible proboscis, ala cone snails, as do the blue ringed octopi of the genus Hapalochlaena. Tiny, beautiful, but more than capable of killing humans via biting.
As tetrodotoxin-bearing pufferfish were mentioned, as an aside, also some newts produce it, newts of the genus Taricha, the red bellied newt, california newt and a couple of others, produce more than enough TTX to off someone.