Rabbit

A rabbit was a small mammal.

Rabbits on Earth
On Earth, rabbits were so prized for their meat that they could inspire poaching, as certainly happened in England around the time of the Great Fire of London. (DW: The Visitation) Centuries later, Ernie Clements, the poacher who worked the grounds of Marcus Scarman's house, caught a rabbit shortly before spotting a robot mummy removing itself from one of his traps. (DW: Pyramids of Mars)

Rabbits were also kept as pets. The Fifth Doctor, Nyssa and Tegan once met a boy named Rithros who had lost his pet rabbit. The Doctor used his celery stick to lure the animal back to his master. (ST: Goths and Robbers)

Boa constrictors preyed on rabbits and ate them whole. (DW: The Time Monster)

As slang
The Fourth Doctor once asked K9 if he wanted to chase some rabbits. Adric had to explain to him that this meant they were going somewhere. (DWAN: Inter-Galactic Cat)

"Rabbits!" was a favourite expletive of Tegan Jovanka. (DW: Logopolis, etc.)

Extra-terrestrial rabbits
C'rizz and the Eighth Doctor once encountered some rather large rabbits on Caerdroia. At the time, the Doctor told C'rizz that there were rabbits on Gallifrey, as well, but they were "rounder and cuddlier" than Earth rabbits. (BFA: Caerdroia)

According to the Third Doctor, a giant rabbit was a delegate at the Third Intergalactic Peace Conference. (DW: Frontier in Space)

On Dagomere, giant rabbits were known to dig large tunnels. (BFBS: The Tree of Life)

While trapped in an Alice in Wonderland-inspired reality, one of the characters encountered by Peri Brown was a version of the story's White Rabbit who strongly resembled the Sixth Doctor. (DWM: Salad Daze)