Key Codes is a little utility that displays the key code, unicode value, and modifier keys state for any key combination you press. If you're a developer, this might be useful to you.
What's new in this version:
Version 2.0 of Key Codes is Many Tricks' first retinaized application (Moom and Witch will be next, and will hopefully be approved for sale shortly; stay tuned for news on that front.)
Beyond support for retina display Macs, Key Codes 2.0 will keep the last entry visible as you scroll back through history, and includes a handy Clear button. Direct versions now include Sparkle, for easy in-app updating.