Dwarf Fortress [official site] has been donation funded since 2007 and according to its monthly status updates regularly pulls in more than $3000 each month. It costs a lot of money to develop and distribute the beguiling dwarven strategy game, however, and perhaps you've been one of the people wanting a new way to toss optional dollars in its direction. In which case, good news: Bay 12 have set up a Patreon for the game.
Patreon is a crowdfunding service but unlike Kickstarter, which is designed for one-off payments for single products, it's designed to support the creation of ongoing works. Web video series, podcasts, and daily pieces of writing and art all use the service. In the case of Dwarf Fortress, your money helps fund a decades-long development project for a grand, unprecedented strategy game. Currently, the 26th best strategy game of all time.
Funding through the service is offered alongside rather than instead of the existing send-us-money-on-PayPal method and entitles to you the same rewards. $1 a month means your name will be listed on the "Hall of Champions" on the Dwarf Fortress website, and you'll be able to choose between a short story reward or a crayon drawing inspired by the creatures in the game.
In case some sort of disclaimer is needed: when the Patreon launched yesterday, I pledged $5 a month to the continued development of the game. Just its regular development notes justify that price to me.