The males of the extraordinary semi-aquatic mammal - one of the only kind to lay eggs - have venomous spurs on the heels of their hind feet.
The poison is used to ward off adversaries.
But scientists at the University of Adelaide and Flinders University have discovered it contains a hormone that could help treat diabetes.
Known as GLP-1 (glucagon-like peptide-1), it is also found in humans and other animals, where it promotes insulin release, lowering blood glucose levels. But it normally degrades very quickly.
Not for the duck-billed bottom feeders though. Or for echidnas, also known as spiny anteaters - another iconic Australian species found to carry the unusual hormone.
Both produce a long-lasting form of it, offering the tantalising prospect of creating something similar for human diabetes sufferers.
Lead researcher Prof Frank Grutzer told the BBC's Greg Dunlop why the researchers had decided to look at the platypus and its insulin mechanisms: "We knew from genome analysis that there was something weird about the platypus's metabolic control system because they basically lack a functional stomach."
They are not the only animals to use insulin against enemies. The gila monster, a venomous lizard native to the US and Mexico, and the geographer cone, a dangerous sea snail which can kill entire schools of fish by releasing insulin into the sea, both also weaponise the chemical.
"That's obviously something that can be powerful in venom," Prof Grutzer said, though he stressed it was not what had led them to the discovery. "It was really coincidental," he said.
He emphasised that much more research was needed before the discovery could, if ever, lead to a human treatment: "An important experiment is going to be putting this it into mice and see how it affects blood glucose levels. That's certainly very high on our priority list.
"But to get to a drug is a very long journey. We still have to learn a lot more about how this platypus hormone actually works."

The film follows versions of the three previous books in the Narnia series.
The Lion, the Witch and the Wardrobe came out in 2005, followed by Prince Caspian in 2008 and The Voyage of the Dawn Treader in 2010.
Sony-owned TriStar Pictures is joining The Mark Gordon Company, The CS Lewis Company and Entertainment One to make the film, according to Deadline.
Together, the previous three films in the Chronicles of Narnia series have made more than $1.58 billion (Â£1.2 billion) at the worldwide box office.
David Magee, Oscar-nominated screenwriter of Finding Neverland and Life of Pi, is reportedly working on the script.
According to Mark Gordon, the film will "introduce this new, magical chapter of the Narnia franchise to fans around the world, both old and new."
The Silver Chair sees Eustace Scrubb - the character Will Poulter played in Voyage of the Dawn Treader - return to Narnia.
There he and a classmate, Jill Pole, embark on a quest to find a lost prince who is being held captive deep underground.
Doctor Who actor Tom Baker and Star Wars' Warwick Davis were among the cast of a six-part BBC adaptation first shown in 1990.
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19 September 2016 Last updated at 07:50 BST
They used recyclable materials such as shoe boxes, plastic packaging and egg boxes to make them.
They went to see how a team from Swansea University are building a real classroom for the future, whose aims are the same.
Their classroom is designed to be energy positive - that means they don't have to buy electricity and they have solar panels that use the sun to power them.
Platypus venom could pave the way for new treatments for type 2 diabetes, say Australian researchers.
[NEXT_CONCEPT]
CS Lewis's magical realm of Narnia is to return to the big screen with a film of his 1953 novel, The Silver Chair.
[NEXT_CONCEPT]
Kids in Swansea have been showing us their designs for buildings for the future, which they say should be as energy-efficient and kind to the environment as possible.