free open source game

Hedgewars – free multi-platform game similar to Worms

If you were born in a generation where Worms was considered a near equivalent to Mario, then you might want to check Hedgewars. It's basically the same game except that you are not a worm and it works great in most platforms. Old versions of the Worms game won't work at all on Vista and most of the current systems today. Even though it's essentially a Worms clone, it is awesome. It features really smooth gameplay and graphics are pretty good. Plus, it will definitely give players a great time.

The Battle for Wesnoth – free & open-source turn-based strategic game

Itching to find a new game, polish your strategy skills and play against others online? Here's an open-source turn-based strategy game with a fantasy theme - Battle for Wesnoth. Battle for Wesnoth might not have the fancy graphics as other commercially available turn-based computer games, but it is definitely a smart, engaging and a lot of fun to play.

Tremulous – not your typical alien first-person shooting game

Tired of your old first-person shooting game which seems to be so repetitive as you go through it day by day? Or perhaps you can't just get over the thought of shooting aliens or maybe you want to fight as an alien this time? Then maybe this is just the game for you. Tremulous is an open-source game for Linux and Windows with a team-based gameplay where players can choose between aliens and humans. It combines FPS with real-time strategy to keep the excitement going on for hours and hours.