There are plenty of documents listing all the APIs and features that Silverlight Windows Phone 7 applications can implement. Here, I would like to reference a few of them that are exclusive of Windows Phone 7 and not (yet?) available on other phones in the same form.

The Pivot and Panorama controls.

An easy one. Not very much to say except, just use them.¨

IIS Smooth Streaming, Smooth Streaming Media Element, Silverlight Media Framework

If you want a great video streaming experience on your mobile device, Windows Phone 7 is your device – And IIS Smooth Streaming the technology to use to achieve this great user experience.
On Sept 24, the IIS Smooth Streaming Client 1.1 was Release To the Web – You can download it here, from which you can read the following:

The IIS Smooth Streaming Client allows you to build rich IIS Smooth Streaming experiences for both on-demand and live IIS Smooth Streaming. This release of the IIS Smooth Streaming Client 1.1 allows you to build Silverlight® players for on-demand and live Smooth Streaming, with full DVR, live ad insertion, multiple camera angles, trickplay, and other rich functionalities. This kit is intended to aid your development of rich Smooth Streaming players and experiences.

The IIS Smooth Streaming Client APIs provide an easy interface for developers and designers to create rich Smooth Streaming experiences using the Silverlight platform. These APIs provide support for simple operations such as Play, Pause, and Stop and also more complex operations such as scheduling advertisements, selecting and tracking bit rates for Smooth Streaming playback, and many more.

The IIS Smooth Streaming Client 1.1 release now includes support for Windows Phone 7.

NB: IIS Smooth Streaming Client is used in the Microsoft Silverlight Media Framework (SMF). This partnership facilitates faster player development.

Great Example: Swisscom TV Air application, available to Swisscom clients through the Windows Phone 7 Marketplace

Hub Extension

Considering that we were just discussing the video experience, another nice feature is the possibility to integrate the videos just played into the “Music and Videos” Hub, the place where all your music and videos are.
With a few lines of code, you will have access to the video material that you have watched or started watching within your application also in the “Music and Videos” Hub, which can even remember how much of the video you have already seen.

More Information, here.

Deep Zoom

Do you want your users to “navigate” high resolution pictures? Windows Phone 7 allows you this thanks to Deep zoom technology.
If you have already seen Schweiz Tourismus Deepzoom Zermatt on the web, you can now enjoy the same application on Windows Phone 7 (Use this Deep link, if you have the Zune Software installed).

More information under http://www.mobiletechworld.com/tag/deepzoom/ which also includes another application developed by Ronnie Saurenmann (Microsoft Switzerland).

Recently, a WP7 Deep Zoom Reader was also posted on msdn.