Well besides the 3 default ones Internet Explorer, Windows Explorer and Windows Media Player (which of course you can un-pin). Out of interest what else have you got pinned to your taskbar in Windows 7?
Personally I have added:
- The snipping tool
- Windows Live Writer
- Winpub ( this is an internal tool)
- Sticky notes
If you want to learn a little more about how to pin new items to your task bar watch this video.