By 'eck that's some fearsome looking moggie. It's a powerful image in it's own right but one that it's possibly a black and white cat anyway and consequently not obvious that it is desat. I will vote high for the image itself anyway. Good luck
I like the shot, nice sharp eyes, but I think a slighter wider depth of field (to encompass the detail on the nose and hairs around it) and a cat with a colour that made more of the desaturation might have improved the image.
I don't think square crops work well with faces...makes them look fatter/bigger than they really are. I do like the B&W treatment you gave it though...and the eyes look very good...very sharp.