Boomslang - Bucephalus viridis [now Dispholidus typus]
Where the elapids and viperids have fangs at the front of their mouth for easy envenomation, boomslangs (a member of the Colubrids) are equipped with regular teeth at the front of their mouth, and venom-injecting fangs at the back. Because of this, even though their venom is extremely hemotoxic, they rarely are able to inject enough into a larger animal (such as a human) to cause death.
However, the bite of a boomslang is not to be underestimated - as it’s not always clear when the fangs have punctured the skin due to the other teeth leaving puncture wounds, medical help should always be sought out. The venom is almost completely hemotoxic, and the lack of neurotoxic symptoms can lead bite victims to believe that there was either no envenomation, or that they can just wait for their body to process the toxin.
This mindset is what led to the 1957 death of esteemed herpetologist Karl Schmidt. He believed that the amount of venom he received was negligible, but 28 hours later his blood was so thin that it was coming out of every hole in the body, including his eyes and ears[!!!], and no amount of medical treatment could have saved him. Early antivenin administration is critical.
Luckily, even if you’re in its natural habitat (forested areas in sub-Saharan Africa), you will probably never encounter a boomslang in the wild. They’re timid, generally dwell in trees more than 20 feet above the forest floor, and would much rather eat a small bird than waste their venom on a human. Most bites occur when someone tries to handle or kill one.
Illustrations of the Zoology of South Africa: No. XXII. Andrew Smith, March 1845.