I always struggle to remember particular keyboard shortcuts for Visual Studio – there are just so many!
The most common ones we use are
Ctrl + K + C (Comment)
Ctrl + K + U (Un-Comment)
Ctrl + K + D (Format Document)
There is a complete list of all Visual Studio shortcuts that is really useful on http://www.shortcutworld.com/en/win/Visual-Studio_2010.html
