Gila monster. Although the venom is a neurotoxin as toxic as that of a coral snake, it produces only small amounts. The Gila monster's bite is normally not fatal to adult humans. No reports of fatalities have been confirmed after 1939, and those prior to that year are suspect due to the primitive dangerous "treatments". The Gila monster can bite quickly (especially by swinging its head sideways) and hold on tenaciously and painfully.
Mexican Beaded Lizard (Heloderma horridum) is a species of venomous lizard found principally in Mexico and southern Guatemala. Along with its congener, the Gila monster (Heloderma suspectum), it is the only lizard to have evolved an overt venom delivery system, and has long been considered the only venomous lizard. The beaded lizard is larger than the Gila monster but has duller coloration, black with yellowish bands of differing width depending on the subspecies.