1. quick silver.
start an application.
option+space.
2. Command+S can save files in almost any application.
3. Command+Option+ESC will bring the force kill box.
4. When Apple Mail hangs with GMail Recovered Mail
This can happen when you send large messages and something goes wrong.
The solution is described here
Delete the hidden directory,
~/Library/Mail/IMAP- @domain.tld@imap.domain.tld/. OfflineCache
and then delete the 'Recovered Messages' mail folder in Mail.app
5. To hide all windows except for the current window do Command+Alt+H
6. In terminal, open fname will open the fname in the default application. If you want to open with TextEdit do open -a fname.