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If you press some keys you use for shortcuts (like Alt or Ctrl+Alt) you get a window which displays a keyboard. On the keys of this keyboard is written, which application will be started if you press this key additional (So if you press Ctrl+Alt (and hold on) you get the window and on the key K stands "K - Kopete", now you press K additional and the windows disappears and Kopete starts. If you finish pressing Ctrl+Alt without pressing K or something else the window disappears, too).
It would be good for people who forget shortcuts.

My TI-89 graphing calculator actually has this. It is quite useful, even though it has far fewer keys.

+1!