One of the most annoying thing is in OSX is when you are watching a full screen movie and an email notification slides in.
Notifications, in general are great, but sometimes, you want to temporary disable them.
Easy. Click on the option key while you mouse click the right pane notification bar.
When notifications are on, the icon will be back to black. You can easily toggle them on-and off.
It took me a while to actually look this up. I've been dealing with notifications interrupting my VLC video watching far too long.