The guilt that comes up (especially around Christmas, etc, but also between Birthdays) where one feels that they must buy someone a gift because that person bought THEM a gift.
This is often despite the person's insistence that "Oh, you don't need to get me anything :)", which usually just increases guilt.
James: Matt bought me a gift.
Calum: That's nice.
James: Yeah, except now I have total giftguilt because I haven't bought him ANYTHING. And I'm nearly out of money...