I'm surprised no one's mentioned this yet ... maybe it's too obvious, but I'll throw it out there anyway:
The Komodo Dragon
The largest lizard in the world, it can top 10 feet in length and weigh in at up to 200 pounds. Its inch-long curved and serrated teeth and powerful jaw muscles help complete the picture of a fierce predator that might consume a meal equaling a quarter of its own body weight. Dinner could be a feast of deer, goat, pig or dog, including meat, bones, hooves, hide and intestines. And this dragon also occasionally attacks humans.
It so happens that the creature's saliva is home to 52 different strains of bacteria, some of them known to be highly septic. If the beast doesn't manage to kill its prey on the spot, its bite will introduce germs potent enough to destroy its quarry with a massive infection within 72 hours. But Komodo observers have witnessed these creatures battling each other, and have noticed that they are never sickened by the bacteria-laden saliva of a fellow dragon.
et cetera, et cetera. I like it because it's real live dragon. With a breath weapon. Not a ranged one, but nevertheless.