I apologize on behalf of my previous (supposed) reply - I think I was hacked. I always import my custom Keyboard Shortcuts file and continue to revise and refine them to accommodate the latest features. I don't use numbers or symbols as that post suggests. Sorry.
By default Revit has shortcuts, for example: 2d mode= 32, Object mode= 3O, Cancel= CG, Delete= DE, Hide Element= HH, Rotate= RO. You should take a look athttp://wikihelp.autodesk.com/Revit/enu/2013/Help/00001-Revit_He0/3032-Customiz3032/3033-Keyboard3033#WS73099CC142F487557BFAA8DA122EC01152F-1289 there they have a PDF file of all the default shortcuts
You import keyboard shortcuts from a text or XML file, you do this by View tab > Windows panel > User Interface drop-down > Keyboard Shortcuts > Import > Select file and open