The most fun I've had has been working on projects like @veloren, watering holes in which people with eclectic interests have come together to poke and experience a public MacGuffin, a commons with all sorts of opportunities for low-level chaos and mischief.
So many aspects of the modern web are locked behind paywalls, API keys, CDNs, etc. Everybody seems to fear their service being taken advantage of, lest it become a victim of the tragedy of the commons.
What if more services were explicitly designed with the intention of becoming victims of the commons?