Cave Story, or Doukutsu Monogatari, is a free Japanese PC side-scrolling platformer/role playing game developed by StudioPixel. It has been translated into English by Aeon Genesis Translations.
The developer, Pixel, spent five years making the game as fun and as great as it is by adding solid controls, smooth gameplay, a great cast of characters and dialogue, an interesting plot, good music and beautiful old-school 2-D artwork. And on top of all this added multiple endings, several boss battles, tons of items to collect, all kinds of added secret bonuses and special challenges, various and considerably different methods of playing through the game depending on your actions, competition ranking features and an extremely high replay value.
The gameplay plays like a combination of various classic games. Some that come to mind are Metroid, Castlevania, Megaman, Mario and Monster Mash.
Its really really polished and for what it is, it is perfect. Simon agrees that it is awesome too.
for more about the game go here [link]
or just go straight to the download [link]