Cats is ambiguous between meaning feline animals in general or the domestic house cat. Either is suitable as a source of roguelike encounters.
In a game that uses pets, a house cat would be a typical starting pet.
Wild cats such as lions, tigers, leopards, cheetahs, panthers, lynxes, bobcats, etc. are fairly common roguelike monsters. These animals tend to be quick predators with a combination of biting and clawing attacks.
The house cat should not be ignored, however. While a modest encounter in terms of combat threat, the cat is associated with magic use and could be given some special game abilities as a familiar. They might be given the ability to see invisible characters (an ability of their larger cousins might also be given).
In ADOM community cats are widely hated because there is incentive to keep them alive while they are generated hostile for most of characters. To make matters worse it is easy to slay a feline without intent to do so.
Mostly found to be member of [f]eline category. Sometimes roguelike cats comes as f of different colors. Bigger ones can grow to upper case (F), beware!