Male platypus is one of very few mammals to deliver venom
Does so from a spur found on its hind limb
Also shrews are said to have a venomous bite
There's the possibility that some moles also have a venomous bite. It allows them to paralyze prey and store them- alive but helpless- for later comsumption. This means the mole's food doesn´t go bad.
The Cuban solenodon is another mammal with a venomous bite.
As for poisonous mammals, how to forget the hedgehog, which rubs toad poison on its quills, and the African crested rat recently found to rub its fur with the poison of a deadly bush to render itself inedible (or at least the worst imaginable snack) to predators.
Here's more stuff:
A skunk's chemical defense is not only foul smelling but can permanently blind an enemy if it reaches its eyes and the fluid isn´t washed quickly enough.
The Asian stink badger has an even stronger chemical weapon; dogs have been said to have died as a result of it.
Giant anteaters do not produce hydrochloric acid; instead, they use their prey's formic acid to aid digestion!
The horny toad (actually a lizard) from North American deserts defends itself by squirting blood from its eyes to the face of its enemy, but its not just blood; it is loaded with formic acid from the ants that make up the lizard's diet.
Moray eels and groupers often team up to hunt; this behavior has been reported separately from the Caribbean and the Red Sea. In one case, the grouper actually kept feeding its old moray eel partner after the latter was too old to help in the hunt at all.
Shrikes are known to mimic the songs of other birds to lure them into an ambush.
Halobates, a kind of water-strider, is the only known pelagic insect.
It lives on the sea surface, feeds on plankton, and lays its eggs on floating masses of algae.
Just as you said about the moray and groupers there is also other teams out there
Coyotes will often team up with badgers that'll dig out ground squirrels and the coyotes will catch the ones that escape from the badger
And also if the coyotes are not around then often or not a Harris hawk or red tail will wait in a tree near by and catch any escapists of ground squirrel
Honey badgers will also be followed by birds that'll eat the leftovers of a raided bee hive
Those birds are called honeyguides and are often say to actually lead the honey badger to bee hives, even tho this behavior has not been confirmed. What is true is that honeyguides do lead humans to bee hives, and even have a special vocalization to "talk" to humans that they don´t seemingly use for anything else.
Once the honey hunters calm the bees with smoke and raid the hive, they usually leave pieces of comb with bee larvae as payment to the honeyguide.
Local belief says that if you don´t pay the honeyguide for its services, next time it will lead you to a deadly animal's lair.
And as if this wasn´t interesting enough, honeyguides also happen to be nest parasites; just like with cuckoos, the honeyguide chick is born earlier than its foster siblings and kills them as soon as they hatch; only instead of throwing them out of the nest, like the cuckoo does, the honeyguide comes equipped with hooked bill tips that allow it to stab its foster siblings to death- all this while still blind and featherless.
Other random stuff:
The spectacled caiman is the only crocodilian able to change its color- although it does so much slower than say, a chameleon.
Rats are known to "laugh" when tickled.
Certain caecilians (legless amphibians) feed their young by growing an outer layer of nutrient rich skin, which the young eat directly from the mother's body.
The hagfish is known to absord nutrients through its skin while feeding inside a carcass.
When raising chicks, some owls will carry blind snakes to their nest without killing them; the snakes are too small to be any threat to the chicks, but they do feed on the insects that are attracted by food scraps in the owl's nest and on their larvae, thus keeping the nest clean and protecting the baby owls from possible infections.
The yamakagashi, a Japanese colubrid, is one of several snakes previously believed to be harmless that turned out to be deadly; it wasn´t until the 80s that the snake killed someone and was finally recognized as dangerous.
However, its venomous fangs are located in the back of the mouth meaning it isn´t very efficient when it comes to injecting its venom; instead, the snake eats poisonous toads and sequesters their toxins, which it can then release from a couple glands on the back of its head. This makes it the only known poisonous snake (as opossed to venomous).
Woodpeckers' pecking subjects them to enormous forces — they can easily slam their beaks with a force 1,000 times that of gravity.The woodpecker's brain is surrounded by thick, platelike spongy bone. They have a large number of trabeculae, tiny beamlike projections of bone that form the mineral "mesh" that makes up this spongy bone plate. These trabeculae are close together to act as armour protecting the brain. The woodpecker's beak contains many microscopic rod structures and thinner trabeculae. It's possible that the beak is adapted to deform during pecking, absorbing the impact instead of transferring it toward the brain. They also have a specially evolved hyoid bone, which reaches from their beak and, unique to these species, loops over top of the skull to completely surround their brains. Also the unequal length of the upper and lower parts of their beaks (the lower being longer), serves to steer the impact force downwards, away from the brain, when it hits the tree.