Take "Doodle or Die," a little game that won the Node Knockout hacking competition for "Most Fun." The game was built in 48 hours, and has extremely simple mechanics. One player draws a picture or provides a short descriptive phrase, and the next player describes the picture or draws a picture based on the description. Players take turns either drawing what's been described, or describing another player's drawing, creating chains of doodles that can take hilarious turns.
Of course, given the nature of anonymity and the Web, right now "Doodle or Die" tends to be full of racism and crude penis drawings, but for every troll there are some artists with a bit of wit, a bit of skill, or a healthy dose of both. And the game is enormous -- tens of thousands of people are playing at any given moment.
So what propelled this simple game's success? Well, the creator thought of a simple mechanic that almost anyone could do -- anyone can doodle a drawing or write a short description, and each contribution only takes a few minutes. And, perhaps more importantly, the game captured the imagination of Reddit, an online community that can generate a tremendous amount of interested traffic in a very short period of time.
There's a wealth of games out there that might not require a full team of creatives and developers months to create. All it takes is a little playfulness and the right audience to create something that thousands of people can engage with.