Here's a list of things that can kill you in Cuba:
SeaSnake (rare)
Shark (kind of common in unpopular areas)
Yellow Scorpion (rare)
Rock Fish (Common)
Everything else, including Snakes, Tarantulas, and whatever else you can think of, only has the potential to scare you but isn't at all poisonous (though
Morray eels can bite, as can
Tarantulas and even
Iguanas they can't kill you as they lack poison. All the
snakes of Cuba aren't poisonous either so feel free to play with all those guys if you don't mind bleeding a little )
Once again, just in case: Avoid the local cats, dogs, and
Hutia no matter how cute they look if you want to avoid rabies.