Good Leader Question:

Interview questions about what was most rewarding and least rewarding can be tricky. You want to make sure that the things you say are least rewarding aren't responsibilities that are going to be a major part of the job you are interviewing for.
When interviewing, always be cognizant of the job you are interviewing for and tailor your response accordingly. Try to accentuate the positive, regardless of what question you have been asked, because you don't want to be construed as someone who is negative about work, in general.