Doing one thing really well

One of my absolute favorite Android apps is Skitch (recently acquired by Evernote). It does exactly one thing: let you doodle on pictures and share them. While they market it for "fun and happiness" I can see applications for maintenance and evidence collection. Skitch is an excellent example of the principle Do one thing and do it outstanding that utilitarian applications should follow. Skitch is available for Android and for the Mac and according to their website for iOS soon.