As a rule of thumb, don't ever buy a woman something she needs. Buy her something she wants, and at best, something she doesn't even know she wants, but will enjoy.

Never buy her anything that is inherently practical. You might like new socks because all of yours have holes, but if you get her tights because all of hers have runs, you'll be the one running...from her wrath. Same goes for kitchen appliances (unless cooking is her passion) or any household items. Let her parents get her contact lenses and car insurance. You get her something that will excite her!