No-op (no action)
From CockosWiki
Sections: Main, MIDI Editor, MIDI Event List (Cmd ID 65535)
Does nothing. If you want a key to explicitly do nothing and you're bored, assign it to No-op. As Schwa put it (freely quoting René Magritte): "Ceci n'est pas une action". Which translates to english as "My hovercraft is full of eels!"