xboxcont Gaming is surely a very big entertainment industry and number of people playing computer games is increasing day by day. Gaming can cost you a lot of money. Other than the hardware for gaming, spending money to buy games is nominal to gamers. Do you know that there are also many free games available that can really rock your world? There are many of them but here I have selected the best 51 that I think you must try because free stuff never sucks. Also most of them are open source so if you are a game developer, you may enjoy having a look at the source.

1)American’s Army 3
An official multiplayer game by US Army. Great game play that has inspired many to join the US Army.

2)Alien Arena
Based on Arenas where Aliens fight. The coolest thing is a large number of players out there playing it all the time . Combines some of the very best aspects of Quake III and Unreal Tournament and wraps them up with a retro alien theme.

3)Allegiance
AllegianceIt’s an online, multi-player space simulation game. Your Spacecraft in spaces flying with other players in team with a fun game play experience.

4)Assault cubers
A first person shooter based on the game Cube engine. Engine is used at full throttle to make the gameplay realistic. This game is all about team oriented multiplayer fun just like counter strike.

5)Armagetron Advanced

A multiplayer 3D game inspired by the movie “Tron”.

6)Battlefield Heroes
A cartoon-style and amazing 3rd person shooter by EA.You can make your own customized player in the game. Graphics are amazing! and game is fun.

7)BlackShot
Multiplayer, FPS (counter strike like) and too good to be free. Maps are urban environments ranging from deserted cities to Arabian Desert tribe lands.

8)Combat Arms
This Multiplayer FPS game has over 3 million players and over 150 guns . Game play is similar to  Counter-Strike, Ghost Recon 2 and Call of Duty.

9)CrossFire
A cross platform multiplayer online computer role-playing game. Has more than 3000 maps to explore and available for multiple OS.

10)Cube 2: Sauerbraten

A free multiplayer FPS, built as a major redesign of the Cube FPS.

11)Dink Smallwood

Old but classic. You will not get impressed by the graphics but it’s isomeric gameplay is so much fun.

12)Flightgear
May people call it Microsoft Flight Simulator Killer. It’s open source and so realistic.

13)Frets on Fire

Guitar Hero like. You can say it’s a rip off of Guitar hero but free stuff never sucks.

14)Glest
A middle age themed 3D RTS with Magic and Tech factions to choose from.

15)Gore : Ultimate Soldier
Classic hard core FPS action with fun and unique gameplay.

16)Hedgewars
Another open-source clone of Worms. Hedgewars is cross-platform and runs on Linux, Windows, and Mac OS X.

17)kde Games
It’s a game package written for the K Desktop Environment (KDE). kdegames provides games in a number of genres including card games, arcade games and board games.

18)Kiki the nano bot

A puzzle game in which a robot called Kiki has to survive in different worlds.

19)KUMAWAR

Another FPS featuring gameplay on the theme of ‘war on terror’

20)NAEV
A space trading and combat game, features many ships and outfits, and a large galaxy to explore.

21)Netrek
Battle simulation with a Star Trek theme. Lots of fun

22)Neverball
Multiplayer mini golf game with so much fun and excitement.

23)Nexuiz
a 3PS that can be played across all platforms.

24)OpenArena
OpenArena is a FPS and multiplayer .It is Quake III Arena style death match.

25)OpenCity

SimCity like but open source and free. Must play if you love city tycoons.

26)Orbiter Space Flight Simulator
image Simply amazing! Simulate from launching a shuttle to landing on moon and beyond.

27)Parabellum
FPS with great graphics and very interesting story. Plot is about a terrorist group in New York.

28)PlaneShift
Role Playing Game in 3D virtual fantasy world. User can explore the virtual world, interact with other players or with server controlled creatures, fight monsters, cast spells, solve quests and puzzles, improve your character, gain magical items and more.

29)PokerTH
Much like Texas Hold 'em rules and betting system. Allows up to ten human players, with computer-controlled players filling in if there are not enough humans.

30)QuakeLive
A FPS game by id Software. A death match like gameplay.

31)RigsOfRods
Rigs of Rods (also known as RoR), is an Open Source 3D truck and car,and boat simulator.

32)Savage2
A fantasy and science-fiction themed game that combines the three elements of gameplay: the first-person shooter, real-time strategy, and action role-playing game genres.

33)Scorched3D
A level of a classic DOS game Scorched Earth. Presents a 3D landscape that features animated jets, naval vessels, water, and even birds, in addition to detailed tanks and projectiles.

34)SecretMaryo

An inspiration of Super Mario. Recommended for Mario fans.

35)Smash Battle
An 8-bit style game where two, three or four player face off against each other.

36)Spring Engine

A free Open Source RTS game engine. Play the game! …its fun.

37)Smokin-Guns
An FPS game. Themed on classic cowboy gun fires.

38)SuperTux A 2D jump'n run sidescroller game in a style similar to the original Super Mario games covered under the GPL.

39)SuperTuxKart

Cart Racing featuring the Linux mascot Tux.

40)The Dino Hunters
An advertisement-supported first person shooter.The story of Dinohunters is centered about a fictitious reality show that sends some celebrities into the past to hunt dinosaurs.

41)ThousandParsec

It’s actually a framework that features space empire building games.

42)TuxRacer

Ice slide Tux, the Linux mascot, and have fun.

43)UFC:AlienInvasion.

A squad-based tactical strategy game with the theme of humans vs aliens.

44)Unknown Horizons

2D RTS with island exploration and town building.

45)UrbanTerror
Urban Terror is a free multiplayer first person shooter developed by FrozenSand. Features an urban terror theme.

46)Vegastrike
imageTrade, fight, and explore in a vast universe with Action 3D. Gameplay features economy, combat and exploration.

47)WarSow
Warsow is An FPS multiplayer with cool graphics. Based on the E-novel Chasseur de bots by Fabrice Demurger.

48)Wormux
Inspired by Worms, wormix is another fun game. Multiple players can play at once with teaming. Can also be played online.

49)WarZone2100
A Tech-Fi RTS that presents a war after world is destroyed by nuclear missles. The game offers campaign, multi-player and single-player skirmish modes.

50)Worldforge
The best thing about this game is the flexible framework though with everyone can contribute their own unique ideas to the project, allowing a multitude of games to be created.

51)Yo Frankie
Developed by the Blender Institute, part of the Blender Foundation. It is based on the universe and characters of the free film produced earlier in 2008 by the Blender Institute, Big Buck Bunny.