Machinarium by Amanita Design
If you've never heard of the Samorost series then you seriously need to open your ears because it is by far one of the most immersive games you'll probably ever play. Go now! Play them for free!
Now back to the topic, Machinarium. The game is similar to the Samorost series in that it is an artistic, immersive point and click adventure game. The attention to detail is amazing in terms of story and the art that makes up the environment.
Now the game isn't out until the 16th October 2009 but you can grab the demo on Steam and I've heard of a rumoured hidden version with an extra puzzle although you might as well wait till the full game comes out.
One of the best elements in Amanita's games is the music by Tomas Dvorak. I would go as far as to say that it makes the games what they are. Tomas has a real talent for making ambience that really reflects the area that you're in. Very powerful.
Overall there will always be some people who won't enjoy it and in a way I pity them because I just feel it's one of those spiritual games where you really feel part of the world, similar to Shadow of the Colossus.
Pre-order it now! Support the indie developers as it's very difficult to gamble and develop such an adventurous game only for it to not sell well!
(Source Image: http://machinarium.net/gallery.html - Date Accessed: 10 October 2009)