I just caused the end of the world. Sorry about that. Although I also died when being driven off a cliff by two girls vying for my affections. And there was the time I spent my life in subjugation to an albino bear. Three of 28 possible endings to Matt Ackerman's Relive Your Life, a flash game that lets you make small decisions that have big consequences.
Essentially a collection of micro-minigames, you're asked to complete quick tasks like repeating a sequence of arrow keys, or typing out a sentence, in order to decide which direction your fate might take. Always beginning with the decision over whether you're male or female, each choice sprouts off another fork of choice, and another, until you reach whichever improbable ending befalls you. After which you're immediately invited to relive your life once more. Which comes a fairly compelling thing to do.
Oh, and it's all told in verse.
It's incredibly silly, the consequences of actions having almost no rational connection, but that only makes it more compelling to replay and find out which other directions it could go in. When choosing whether to help a man with a scorpion on his face decides whether you life your life as a science experiment or as Doctor Who, you know you're not exactly bounded by reality.
Many thanks to Alan Lamb for the spot - you can play the game for free here.