Find My iPhone - When your iOS device has been located, it shows the remaining battery level, so you know if you’re going to lose track of it soon.
OS X - Option-click Sound icon in the menu bar to change sound output and/or input quickly.
OS X - Searching in System Preferences highlights the relevant sections. The more relevant the section, the brighter the light will be.
Dropbox - iOS app automatically pauses Camera Upload when the battery is running low.
OS X - Adjust the volume in 1/4 increments with shift+alt+volume keys.
iOS 6 - When selecting new wallpaper, preview screenshots show a realtime view of your current home & lock screens
/via Rich Cornish
iTunes - When adding a free item to a Wish List, an alert reminds you that you can download it right away.
Mac OS X Mountain Lion Spotlight - Finds Calendar & Contacts even when you type in their old names (iCal & Address Book) from previous versions of Mac OS X.