The first free game I will feature is a little game called Cave Story. Cave Story AKA Dōkutsu Monogatari in Japan is a side scrolling shooter and overall an amazing game that was made by one person (like Minecraft) Daisuke Amaya he worked on this game for 5 years and then made it completely free on the PC. When you download the game its in Japanese but you can just download a patch and make it English in about 5 seconds. In 2010 the game was released on wiiware for 1200 Wii points (or whatever there called) With updated graphic features etc.
Review The basic plot to cave story is the main character (a robot named Pixel) wakes up with no memory of where he is or how he got there anyway when Pixel awakes he finds himself on a floating island populated by creatures called Mimigas. Also growing on the island are red flowers, red flowers make the Mimigas go crazy if consumed and become monsters. The antagonist in the game Doctor is forcing the Mimigas to consume the red flowers and make an army of monsters TO RULE THE WORLD and you must kill him. Of course there's more to the story but I don't want to bore you more than I have to. Like I said its a side scrolling shooter with nice fluent controls throughout the game you will meet new enemy's and healthy amount awesome upgradable weapons the games difficulty starts nice and easy and progressively becomes harder throughout the game. The game has a very impressive storyline witch I did not do a very good job of telling but trust me near the end of the game it becomes EPIC. Overall the game is very impressive and has good replay value with nice boss battles, AMAZING music, sweet weapons and multiple endings (and trust me if your going for the true ending its not easy) My rating is 8.5/10
Downlaod the game and translation patch: http://www.cavestory.org/downloads_game.php
Wikipedia article: http://en.wikipedia.org/wiki/Cave_Story
PC vs Wii game graphics