Btooom!

Sakamoto Ryuuta is an unemployed 22-year-old who lives with his mother. In the real world, there may be nothing really special about him, but online, he's one of the world's top players of the combat game "BTOOOM"!

One day, he awakes in what appears to be a tropical island, though he has no memory of how or why he has come to be there. While wandering around, Ryuuta sees someone and calls out for help. The stranger responds by throwing a bomb at him! Now Ryuuta realizes both that his life is in danger, and that he has somehow been trapped in a real-life version of his favorite game! Will Ryuuta be able to survive long enough to figure out how and why he ended up here?

(Source: MangaHelpers)