Mac OS X - The low battery alert goes away automatically if you plug in first without clicking ok.
OSX - Hitting “Esc” chooses Cancel, hitting “Return” chooses Save, hitting “D” chooses Don’t Save. Allows you to control this menu without using a mouse or trackpad.
/via Andrei Herasimchuk
Skype 5.0 for Mac - Displays an arrow next to a person’s mood message. When clicking on the arrow, all links will be opened at the same time.
Twitter for mac - After typing the first few letters of a word, pressing the ESC key will show a list of words that starts with those letters.
Edit: This is a native feature of OSX and works in some other apps as well.
Mac OS X - When searching in the help menu of an app, the menu relevant to the result is pulled down with a blue moving arrow pointing at the menu item.
/via Stephen Litt Belch
Mac OS X - When doing a calculation in Spotlight, Cmd+C copies the result without having to select it.
Typinator - Menubar icon dims when you activate password / security form fields.
Twitter for Mac - After installing the app, right click on any text in Mac OS X to see a tweet option.
/via Brendan Lee