Gift cards or money are great gifts for a person that has everything. You can get a general gift card from Visa, Mastercard or American Express. Visa and Mastercard gift cards are better because sometimes American Express is not accepted everywhere, it's better safe than sorry. You can get these credit cards at banks, you may be able to find them at stores like Walmart or Target too.
You can ask the person what are his/her hobbies. If he or she like movies you can get a gift card for the movies. If he or she likes to read get a gift card for a book store. Find out what is his/her favorite store and purchase gift card for that store for example if it's Macy's or Walmart get a giftcard for that store. You can also purchase a mall gift card so that person have a choice to go to any store within that mall.
I hope this helps.