Kryptonite.

You can answer this question by either stating a weakness that you encountered during your previous job and how you overcame it, or you could reveal a weakness not at all related to the job profile.Example: At my last job I found that I did not know enough about ............., so I took a night time course to learn more. Or you can say, " I can't leave my desk at the end of the day until it is tidy." Don't say that you do not have any weaknesses, because after all, you are human. This is the quickest way to torpedo your chances. Rather, you should use the approach of converting your weakness into a strength. You will sound confident and resourceful if you are able to recognize your own weaknesses and find strategies to overcome them. For more tips, go to http://www.italki.com/knowledge/page/HOW%20TO%20SUCCEED%20IN%20JOB%20INTERVIEWS.htm

I think I would say something like, my weakness is my tendency to get so engrossed in whatever I'm doing that I lose track of what's happening around me.

I suppose, the best answer would be to tell about your bright sights :P. I mean if you tell that you're over-precise, perfectionist, none can take in negatively. And just skipping that way the troublesome question. However, I don't have a great experience in such 'bussiness' matters, the best idea is just to be careful with everything you're saying ;).