View All Assigned Keyboard Shortcuts
There is a very nice app that's freely available to show you all shortcuts when you hold down the command key a bit longer than normal.


http://www.cheatsheetapp.com/CheatSheet/


It works on Mavericks and several older OS and I've never had problems with it other than forgetting to quit it after I'm done discovering shortcut keys. It appears to be advertisement supported, so consider that if you prefer to pay to support developers as opposed to be part of what's being sold.