Escape from City 17 is a short film series based on the popular computer game, Half Life. It is directed by The Purchase Brothers.

From the youtube description:

The Escape From City 17 short film series is an adaptation based on the Half Life computer game saga by Valve Corporation. Originally envisioned as a project to test out numerous post production techniques, as well as a spec commercial, it ballooned into a multi part series. Filmed guerilla style with no money, no time, no crew, no script, the first two episodes were made from beginning to end on a budget of $500.

For the amount of resources they had to work with, this is amazing! You can see more of their work at their youtube channel.