Select All Unused Key Command
It would be very useful if custom key commands could be applied to palette commands. Specifically, I would love to create a key command for "Select All Unused" in the swatches palette drop-down menu. It currently requires a click in the palette, scroll down to select the command, clicking the garbage can in the palette then clicking (or enter/return) to confirm that you want to delete unused swatches. Some days I convert hundreds of files swatches from Pantone to CMYK then to RGB. A key command would speed this up dramatically!
User since Illustrator 88!
As John says, you can insert this command into an action and use a key to run it.
This does not mean that Ai does not need a native assignable hotkey slot for it, on the contrary, every command in Ai must be :)
John Garrett commented
I believe there's a default action which deletes all unused panel items. I set a keyboard shortcut to it and it runs very quickly with no further interaction.