I'm not sure if this button is the right button for what I'm about to talk about since it would take away the "select" button dedicated for certain emulators, but with a multitasking device, being able to end a program that crashed without powering down the entire device seems important.. We could label it with the Pandora symbol and mix it's options with the multitasking ideas above: It could go back to the main menu, which if it is going to be like Gmenu2X it can have one tab dedicated to running applications (which this button goes to by default), where, if you wanted, you could either select a new running application, or press a sub menu button over that application's icon (or if you were using the touch screen you could just hold your finger on the icon for X amount of seconds for a sub menu to appear) giving you extra options for managing the highlighted program, one option could be "close" for exiting a non responsive program.
Another idea for a menu option could be: "Suspend to Disk" where if you wanted to, you could stop a running program and move it to your SD card freeing up memory for a different program.. like if you were playing a game and your friend came in and wanted to play with the cool new Pandora (and who wouldn't), You could just suspend the game to the SD card giving him all the memory he needs.. has this been done before? (this might be similar to save states in emulators).
To retain the ability to map this button as "Select" for those certain emulators, and to cut down on the accidental pressing and unfocusing of a current application, the button could do only that which the application in focus tells it to do. Only if it's pressed in combination with "Menu" will the button go to the system menu. Actually, this might be a better idea, because when you press "Menu" by itself the program's menu will come up with functions related to that program, but when "Menu" is pressed with the "Pandora" button, the Pandora's Menu will come up.