Black cats are always popular, especially for Halloween.
The basic black catsuit (centre) can be supplemented with an eyemask and ears on a headband. As an alternative, you can
use black and white face-paint for a full-on feline disguise. (Instructions here)
Also, you have the various guises of Catwoman, from the Lycra and PVC versions shown, to the street-fighter crop-top
of the bottom right of the picture.