This would surely depend to a huge extent on what sort of a job you are applying for. If you were applying for a teaching position, for example, you would want to talk about PowerPoint. If you were applying for a job as a secretary, for example, PowerPoint would be much less useful and you would have to discuss your familiarity with programs like Microsoft Word and Outlook.
If this is a generic question such as one for a school senior project (where you don't have a job in mind), you should simply talk about whatever software applications you have used that could possibly be useful for any sort of job at all. I would imagine that the Microsoft Office programs would be your starting point and then you could branch out into anything else (like graphics programs or Photoshop) that might possibly be relevant.