Always wanted to enter a new line into a microsoft excel cell within the Microsoft Office for Mac? It is nearly as simple as on windows on windows you use Alt+Enter an on the Mac you use: Ctrl + ⌘ + ↩ (Control + Command/Apple + Enter)
Again a different behavior for typing an at (@) sign when you are using a Windows (Win7) VM under Parallels Desktop on your mac. I had my problems typing my first email addresses 😉 Ctrl + ⌥ + q (means: Ctrl + alt + q)
If you have the problem that your ctrl-alt-backspace combination does not work and you have to restart the x-server see this blog entry here for the solution or simply go to System --> Preferences --> Keyboard --> Tab "Layouts" --> Button "Options" --> open "Key sequence to kill the X-Server" and enable the checkbox. Done.