A recent release from Indie Developer Lexaloffle Games. Released barely two week ago, it is currently coming to an end with its “Humble Bundle” Offer. Exactly nineteen hours after this post the game will cost $15, but until then you can pay WHATEVER you want. Be it a penny, nickel, Euro, Wampum, anything goes. I personally picked it up for a dollar, but the choice is yours.
Now the game itself. Voxatron is basically Minecraft meets Contra. The game is divided into rooms that are half puzzle, half shooter in a blocky pixelated environment that is completely destroyable. You start with a basic gun but can find packages on floors at various parts of levels to turn it into a cannon, shotgun, or even a block spawner. The game has a decent number of levels with a fair amount of complexity, but is by no means a complete title. It is being updated with new content regularly, so you can expect plenty more playability in the future.
If you have a few dollars to throw around, want to support a promising developer or enjoy old school puzzle platformers, give Voxatron a try.