Bayounikals (or Bionix, Bayoniks) were a giant teknikal race that towered over minifigs. However, they are extinct as of approximately BR 2012. Minifigs that are old and lucky enough to see them have commented on their similarity to robots.
From the Old Wiki:
Dr. Henry von Fireo was a respected Doctor at Hospital 555. As he got older, he became kinder to his patients, as result of becoming senile and the onset of old-age peace. As a result, he was fired post-haste. This caused him to see the error of his ways, and cleared his head of the peace neuro-toxin. He decided to create something he could use to torture those who scorned and fired him, as well as anyone else who got in his way. He wrought giant, clunky, rainbowist-like death robots. These strange robots became sentient, and, true to nature, killed Dr. Fireo immediately. They then went off to terrorize any minifigs that they could find.
They ravaged the countryside, and the stateside, and even the continentside! Eventually, a mysterious BrikWarrior defeated them in battle. They were so astounded by the fact that their red, blue, and green asses had been handed to them that they evolved. They became Grays and Blacks and Whites. They became less intricate, and more cost-effective. This was known as their Silver Age. They never had a Golden Age, oddly.
Unfortunately, they eventually became more primal, growing more and more difficult to build. Eventually, they were essentially walking piles of weapons. This would have been fine, if not for the fact that no minifig could use the damn things. They were around twice as big as a single minifig, and couldn't be mounted on a vehicle. The Bionix were exterminated by the same crusader that had defeated them before. Still, no one knows who this badass was, but many think that Dilanski's Dad did this on his way to save that cat and back. The scattered remains of these robotic creatures are scavenged by others like Dr. Fireo, who use the components to bring about thier own machines of death, albeit these are usually much more controllable. Usually.
Kind of like Teknix, except these were created, the Teknix are living.