Unyuufex is the most tragic Tyranid alive. It is a special breed of Carnifex that wants to hug and cuddle everything, but ends up killing most things as it can't control its own strength.
It is also Abaddon's only friend, hugging the poor fucker when he can't hug anything himself. Because, you know, he doesn't have arms.
It is a known rumor that Lofn may have been the companion of Unyuufex, although that is arguable with the similar theory that Lofn's Tyranid companion is an offspring or genetic clone/brother etc. of Unyuufex. In fact, it is heavily implied by /tg/ canon that Unyuufex is actually Lofn's pet Ripper, all grown up. Or at the very least Ripper is a relative/offspring of Unyuufex. Perhaps there's a whole Hive Fleet Unyuu, comprised entirely of Unyuunids? Oh shi- It is probably that last one, as she has that effect on Tyranids.
Update: Has been introduced to Lenny from of Mice and Men, are now living happily ever after, crushing adorable things with their massive retard strength.
Double update: Vulkan has found one and has indeed, booped the snoot.
"Unyuuuuuuuuuuuuuuuuuu!", the horrendous cry echoed above the battlefield, the Sisters of Kitty ceased the firing of their pink bolters and revered Brother Yuki of the Pretty Marines halted his songs for a second... everything froze, it was as if time itself stopped dead in its tracks. The Tyranids that time and time again broke against the might of the Imperial army all chattered, they clicked their mandibles and the clatter of chitinous plates and insectoid legs was deafening. "Unyuuuuuuuuuuuuuuuuuuuu!" the sound echoed across the field once more, as if coming from within a tunnel or ship, the Tyranids stopped, they stopped in everything, not a sound was heard. The Sisters of Kitty looked worried at each other, the red bows in their pristine white bowlcuts were slightly moved by a gentle breeze. "What is happening," asked Kitty Sister Adiane, "they aren't moving... Was it because of that sound?"
Sailor Kitty Sister Moon looked at Adiane, the tiara on Moon's forehead reflected the few last rays of sun as the blue sailor skirt was moved by the wind, "That sound, Adiane... is why we will not win this day" she said, her face bitter as the wind now latched onto her immensely long, golden braids. "Sailor Kitty Sister Mercury," Moon said, "How long until the creature emerges?"
"Three minutes and twenty four seconds" Mercury replied, her blue visor glistened like ice in the setting sun as data rushed across it and she frantically tapped the keyboard of her small blue handheld computer, "I am sending the data to Battle Brother Cloud of the Pretty Marines as we speak. Prepare the evacuation."
And at once, large lilac Thunderhawks swooped in, guns blazing to clear a landing zone amongst the paralyzed Tyranid hordes, one could only guess that it was fear that had rendered them in such a state, quivering statues, frozen in time.
As the last few Sisters of Kitty and Pretty Marines rushed onto the ships, the cry was heard once again, "UNYUUUUUUUUUUUUUUUUUUUUUUUUUUUU!" stronger now, and in the distance, one could see a wave of panicked Tyranids, running from something, and behind them, an ever increasing cloud of eviscerated blood and bodyparts, as the frantic, tragic whelping and whimpering of "UNYUUUU" echoed across the battlefield.
"What are those?" Kitty Sister Adiane said, "Unyuufexes," a strong voice said behind her, it was Sailor Kitty Sister Mars, her hair long and black, her sailor dress in blazing red, and at her armoured hip, a still warm hellpistol, Adiane also noticed the heavy flamer slung across one of Mars' shoulders, "there is nothing more for us here" Sailor Kitty Sister Mars continued, "We have called in the only ones able to deal with this problem."
And with that, as the growing cloud of blood and Tyranid limbs came ever closer, a huge, vox assisted roar split the skies, "FIGHTING UNYUUFEXES ISN'T MADNESS! WHO THE HELL DO YOU THINK WE ARE?!?!!!!!!!!".
And with that, a huge, forearm-and-fist-shaped battlebarge with a prow more resembling a gigantic finger than anything else, rushed through the outer atmosphere and tore through the air, and then landed amongst the fleeing Tyranids in a hail of gore and dust.
"Bass Jackson and Brother Kamina will take care of the beasts." Sailor Kitty Sister Mars said as she went into the ship, Adiane followed her, and through one of the viewports, she could see two massive, yellow-armoured figures stood in the sunset, opposing them were a host of drooling, googly eyed Unyuufexes, their claws covered in the remains of their hugged victims, the ground around them was empty, the normal Tyranids had already fled past the horizon.
"Feeling lucky today... punk?!" Bass Jackson said, the Unyuufexes drooled for another second, and then, as one, shouted, "UNYUUUUUUUUUUUUUUUUUUUUU!" and charged toward the two Angry Marine Commanders.
(Story copy-pastaed from warseer.com, courtesy of Neknoh)