This is a really good 'trick' question. Though it seems innocent enough beware when you're asked this during an interview. Why - you may well ask? Firstly people don't generally expect to be asked this question and consequently are thrown off their guard when asked. Secondly, for those (and that's most of us) who've been unfortunate enough to have had awful jobs in the past - it can provide the impetus to set you off down a negative path whilst you slag off your previous employer/job. And although your previous boss or job might have been awful - it's on a need to know basis and this is not something an interviewer needs to know.

What to say: Again it's always best to try and stay as neutral as you can and avoid getting sucked in talking negatively about ex employers/jobs. Responding as follows (using your own language of course) will help keep you out of trouble.

"Of course we've all had jobs that didn't work out as planned but nothing really springs to mind that I could classify as the 'worst job'. Generally I've found that even if I didn't enjoy doing something, as long as I was learning or being challenged then it was a good experience".

This should be enough for the interviewer to move on but if they decide to pick on the 'jobs you didn't enjoy doing' - stick to your guns, simply smile and say "gosh nothing immediately springs to mind, sorry" and then keep your mouth shut!! You'll find with this the interviewer will definitely move on!