Detecting the Backspace, Enter, Tab, Escape, and Delete Keys using hacked key pressed blocks. The Special Pressed? one lets you know that 'any' non-ascii key is pressed (i.e. shift, ctrl, alt, F1-F0, etc) Thanks to @cobraguy for that! One word of warning, I believe the Scratch Team intend to make the Enter Key be the equivalent of clicking the Green Flag... If that goes ahead, then obviously using the Enter Key in your projects may not be such a good idea. The same already stands for the Escape key ;)
100% to Griffpatch!