If you're looking for an addictive yet challenging puzzle game on Windows 8, I'd suggest you take a look at the new New 4 Pics 1 Word. The game can literally make you scratch your head for sometime to find the right answer to a given question, actually a set of pictures.
As the name of the game suggests, it will display four pictures on the screen which will have one thing in common, and it's your task to guess it correctly. Additionally, they'll make it easier for you by giving you empty boxes that represents the characters in that missing word, along with a bunch of letters to choose from. The game comes with over 1,000 challenging levels, and you can continue to play the game as long as you complete each level, which tends to get more difficult as you move on.
In case you're unsure about anything, you can use hints in any given puzzle, but it will cost you hint coins. You get extra coins as you complete levels, and hints cost 50 coins. You also have the option to delete the word for an additional 150 coins and move on to the next puzzle. If you're looking for some extra pile of hint coins, just review the application in the Windows Store, and you'll get 2,500 hint coins.
On a side note, New 4 Pics 1 Word is an extremely popular puzzle game on various mobile platforms, including iOS, Android and Windows Phone with over 100 million players across the globe. However, this is not created by the same developer and appears to be a third-party game, but with a similar concept for Windows 8.
If you're ready to take up the challenge, head over to the Windows Store and grab the application -- its free of cost.