Generally there are two main reasons why people dislike certain tasks. The first is that they do not feel confident about carrying them out, the second is that they believe such work does not use their full potential. Work out which of these reflects your situation and be clear about what you mean by the worst jobs.
What is it that you dislike about the tasks you are being asked to do? Are they too hard or too easy for you? If you feel they should be done by someone else, consider who that should be and why it would be a more appropriate assignment for them. Then think about the work you would rather be doing and how you could justify your suitability for it. Finally do some soul searching – thinking about why you end up with these jobs. Is it because you have a real flair for such work or because your boss does not see you as being capable of doing anything else?
Before discussing these issues with your manager be sure you have a firm idea of what you want the outcome of such a conversation to be. Whatever your goal, avoid making any exchange sound like a complaint. You will get more interest and support if you can show how altering the composition of your working day is going to benefit the organisation. Presenting problems often generates resistance, showing you have analysed a problem and come up with a series of solutions is much more effective.