How do you refer to cats?

[udarnitsa.livejournal.com]

Let’s say you’re walking down the street and see a cat. You want the cat-lover you’re walking with to see it, so you point at it and say, “Look! A cat!” What word do you use? Кот? Кошка? Котик? If you know the sex of a cat, do you automatically use the correct word?

English doesn’t force us to specify gender the way Russian does, so I find this confusing.