For this answer, you should display a weakness that can be seen as a strength. There are many types of answers that will work. Some answers will be good answers for certain jobs, while the same answer will be a bad answer for a different job. Select an answer that will work for the position you are applying for. Here are a few examples.
Both of these examples show an answer that is acceptable. Although being impatient is not good, it shows that you are a quick learner and that you like efficiency. The second displays a person that is detail oriented, which can be seen as a good trait. Finally, both answers identify the weakness and show the actions of correcting it.