The indie game community is now the place to look for game innovation. Sometimes the experiences might be too experimental, but other times, you'll find new game mechanics that are just really cool (like the highly rated Braid).
Munky is a little platformer puzzle game that takes a fairly simple concept and makes it quirky and original. You control the Munky, and have to guide it to the exit of each level. Every exit is locked and can only be opened when a block is placed over a pressure switch.
The unusual mechanic is that Munky can carry a huge block in his stomach, and reproduce it at will. The animation of Munky swallowing the block is worth a download itself! As the game proceeds, keys, gates and multiple switches are introduced, making it more and more complicated.
The graphics are pretty basic, and the sound is enjoyable, with suitable music, and great retro sound effects. The only criticism of Munky really is that it is pretty short, but it's free too so it's hard to complain! The platforming itself is pretty unintuitive - you actually move around block by block, and jumping is not done in the traditional Mario way - if there is nothing to jump onto, Munky will not respond.
Munky may be short, but it's a cool and pretty innovative platform puzzler that's a great way to pass some time.