On the bottom of different blocks will be pieces of paper with gift card amounts - usually $25 with some $50s sprinked in. Can do it once a month and then it'll reset at the beginning of the month. If you knock it over, you have to bring in donuts for the office (on the company's dime).

For some reason only a handful of us participate each month - it's literally free money, and 2/3 of the office doesn't care.