In your Mac login window, you can add a welcome message right below the Apple and System Status. You only need to perform this following command line:
sudo defaults write /Library/Preferences/com.apple.loginwindow LoginwindowText "Hi, I am Mac"
Characters inside double quote will be displayed as your welcome message. I know you will try this and I also know that you will want to delete it as soon as you've finished trying. So, here is the command line to delete your Mac welcome message:
sudo defaults write /Library/Preferences/com.apple.loginwindow LoginwindowText ""
Someday, you can consider putting your username and password as the welcome message. No one will know, except me, you and other readers of UsingMac.com.
Everytime you have incoming message to your Mail, you will realize that there is a sound echoed by your Mail. This sound is set as New Mail Sound by your Mail default. The fun thing here is you can set this incoming Mail sound with custom sound.
Do you want to this setting custom Mail sound can be done?