The Plague Star, by George R.R. Martin (of A Song of Ice and Fire fame) featured creatures called "hellkittens." These were much like the Arduin "killkittens" (see their entry in the Tabletop RPG folder). Except rather than secreting their paralytic venom through hollow claws, they spat it in wads of powerfully acidic saliva.
Another literal killer rabbit is the Miraj (also rendered Al-Mi'raj, or various other variations on the two) of Islamic/Arabian poetry and folklore. A yellow rabbit with a single large horn, it can kill and eat things much larger than itself. It appears in early editions of Dungeons & Dragons — with a third-party company porting it to 3e — where some of them have Psychic Powers. It also appears in Dragon Quest where, due to the translators apparently flipping coins, it's sometimes called the "bunnicorn".
Margaret Atwood's Oryx and Crake includes wolvogs, creatures that look like friendly dogs, and when they are not ruthlessly killing other creatures, they act like friendly dogs. They can go from friendly to homicidal, and back, quickly.
Bunnicula has a vampire-like rabbit that Chester assumes is a killer rabbit, but there's no evidence that he ever actually does any harm whatsoever besides draining vegetables.
Norska in the Dragaera series are omnivorous rabbits that eat dragons.
In Terry Goodkind's Soul of the Fire, an embodiment of evil either possesses or impersonates a chicken. Strangely, the main characters are capable of realizing this... which means you have two badasses who rule the known freaking world and who can alternately make people her slave or destroy armies with a wave of his hand scared shitless by a goddamn chicken.
In the Robert Heinlein juvenile Tunnel in the Sky, a group of teenagers on a survival-training exercise are stranded on an Earthlike planet when the wormhole they used to get there malfunctions. One local animal is the "Dopey Joe", a stupid, slow-moving cat-sized reptiloid which appears utterly harmless... until the season comes when it, well, swarms.
Redwall: EULALIA! And that's just the badgers. The other species like hares, mice, otters, squirrels, hedgehogs, and even moles are also quite capable of fucking up the shit of any vermin that threaten them. (Although a badger isn't exactly in a Killer Rabbit scenario when what it's fighting is a rat.)
Watership Down: Gen. Woundwort, who can fight (and beat) many of the beasts that prey on rabbits. As opposed to Bigwig, who is One Badass Rabbit. Also of mention would be the Black Rabbit of Inle, the most extreme version of this Trope, being he's basically the Grim Reaper in rabbit-form.
The bunnydogs from The War Against the Chtorr series by David Gerrold appear to be the only friendly Chtorrans encountered by the humans. Unfortunately they also represent humanity's future in the Chtorran ecology: as passive, contented creatures who are glad to be eaten by higher members of the food chain. There are also meeps. A mother rabbit will reject her own young to nurse meeps, who will then suckle her to death. One character darkly theorizes that the excessively cute bunnydogs are meant to be the equivalent for humans.
Mr. Rabbit from Rainbows End qualifies as "the next bad thing" in the eyes of one expert character. The previous "bad thing" was a plague worse than bubonic, and the one before that was the nuclear destruction of Chicago. It's never made clear how much rabbit-nature he actually has.
The political satire The Year of the Angry Rabbit by Russell Braddon. The rabbits are infected with a highly toxic (to humans) strain of myxomatosis. Rather than trying to wipe them out however, the Australian government is more than happy to possess the most feared biological weapon in the world. Was the inspiration behind the classic B-MovieNight of the Lepus.
The Edge Chronicles is covered in The Lost Woods and full of all manner of horrific animals and plants, but the effectively undisputed top of the foodchain are Wig-wigs. Small, orange fluffballs that also happen to be pack hunters that can and will kill anything they can reach, no matter how big or strong it is. Their only real weakness is their inability to climb.
Most of the "Furies" from the Star Treknovel series "Invasion" resemble demonic creatures (because they're the beings that spawned the legends). A few, however, are fluffy and cute. They're still vicious killers who want their ancestral home back, though.
Barbara Hambly's Star Trek novel Ghost-Walker features a race of diminutive fluffy bird people who are mostly ultra peaceful and sweet. Mostly. When one particularly xenophobic one gets nasty, he uses his monstrously powerful telepathy to drive an entire invading force of Klingons to suicide, Mind Rapes and possesses Captain Kirk, and almost destroys the Enterprise before he's convinced to stop.
Treecats in David Weber's Honor Harrington series are cute, fluffy, six-limbed felinoids who are great with children, wonderful, supportive companions for life who'll be with you through thick and thin... and will turn into fuzzy, flying buzz saws if they think you're a threat to their kittens or adopted humans. Treecats think that enemies come in only two states: those that have been properly dealt with, and those that are still alive.
They are also a race of The Empath, so don't bother trying to sneak up or wear a disguise. If you want to harm their adopted human and come within 50 feet, prepare to get your throat ripped out.
In China Miéville's The Scar, the head of Armada's underwater police force is a sadistic dolphin named Bastard John.
The Sten series has Doc, an alien who resembles a cuddly koala bear. His species are in fact vicious predators which act cute to lure in prey; Doc is so bloodthirsty that he has to be fitted with a Restraining Bolt in order to interact with his teammates without killing them out of instinct.
In The Hunger Games, there are carnivorous squirrels, poisonous butterflies, killer monkeys, and much much more.
In the Star Trek: TNG novel "To Storm Heaven," a B-plot involves Alexander (Worf's son) receiving a hamster from Dr. Crusher as a pet. Worf starts off contemptuous of the sleepy little beast, until he mishandles it and gets the hell bitten out of his finger for his trouble. Worf actually respects its Killer Rabbitness and names it a Klingon name that means "Tribble who battles with honor". Alexander prefers the original moniker of "Fido." Of course, hamsters come from Earth, where most everything not obviously dangerous is probably this trope.
One of Derk's experiments in Dark Lord of Derkholm resulted in an entire flock of carnivorous sheep. This was apparantly an accident, but it comes in handy when his children need to keep an army of dangerous criminals in line.
Partway through White Fang, the title character is thrown into a dog-fighting ring. He kills everything sent at him, even a lynx... until the ring owners bring in a bulldog. A remarkably friendly bulldog named "Cherokee" who at first doesn't attack. It nearly kills him.
On one of the unknown islands visited by Mael Duin and his companions in the The Voyage of Máel Dúin, the voyagers discover a mysterious palace inhabited only by a playful kitten. Everything is fine until one of them tries to take one of the precious necklaces from the piles of treasure lying around; which is when the kitten jumps at him and burns him into a heap of ashes. Then it goes right back to his play.