Grand Theft Auto
In this online version of Grand Theft Auto, the plot is basically the same. You are a random (and customizable) dude on the streets who is looking for money. Explore the streets of the city, beat up whoever you can, and collect a vast array of weapons. Intimidate those who dare come to close. Although not as good as the Xbox/PlayStation/PC version, this flash game version still brings some of that renowned crime.
See the beginning of the game for a tutorial.