The official Google app for Windows Phone gives you quick and simple access to the world's favorite search engine.
Of course, Windows Phone comes with Bing integration built in, but for many people, me included, Google search results are more reliable and relevant.
The Google app lacks some of the advanced features of the Bing app (barcode scanner, music discovery, music history, etc.) However, you can filter results by web, images, places, news, videos and blogs. Like Bing, the Google app includes a voice search function.
It's possible to turn on geo-location in the Google app for Windows Phone, which helps you get more relevant results depending on where you are.
Although essentially just a shell for the mobile version of Google, the app is clean and easy to use, with a very simple layout.
Although it lacks some features, the Google app is worth pinning to your Windows Phone start screen to get quick access to the greatest search engine.