Headphones are an important part of your home studio, whether to track and record audio or to mix down audio, especially if you don't have good quality studio monitor speakers. If you spend a little more on the headphones, you may not need speakers, although good quality monitor speakers are always recommended. Sometimes you just don't have the space or budget for studio monitors.
I use the AKG headphones.
For mixing use I recommend something with a flat frequency response (no boost or cut in any frequencies).