Each of us has some preferences. Someone loves webdesign, someone else is into designing clothes, or buildings. Some guys prefer to be involved in product management, having a role of a designer while taking care of the entire product cycle.
However, you should forget your own interests for a while, and think about the interests of an employer. You should say that you like to design the things they typically design in their company.
Needless to say, you have to do your homework before you can find the right answer. Spend some time on their website, check their portfolio, find out what they are into, and stick to that in your interview answer. Job description will also help you to find out more about their designs.
Remember that it is tiring and dreadful to work on projects you don’t like. I would suggest you to apply only for those designer roles which you will enjoy doing….
I like webdesign, especially designing sites for mobile devices. I would love to specialize in this field, that is mobile responsive design. It is also one of the reasons why I decided to apply for the job in your company, becasue I know you’re into the field.
I love creative design, and I really enjoyed browsing your portfolio. I saw a lot of creativity in each piece of work, in each campaign you run.