One of the most obscure keyboard shortcuts has got to be Shift+F8, which is used for listbox discontiguous extended selection. Man, what a mouthful. KB article Q301583 doesn't help matters by listing this keyboard shortcut under "Dialog box keyboard shortcuts" even though it isn't a dialog box keyboard shortcut. It's a listbox keyboard shortcut.
If the listbox supports extended selections (via
LBS_EXTENDEDSEL), then you can use the Shift+F8 shortcut to create discontiguous multiple selections from the keyboard. (Via the mouse, you can just Ctrl+Click to create a discontiguous multiple selection.) Type Shift+F8 once to enter extended selection mode, then use the arrow keys to select an item and press Ctrl+Space or Shift+Space to select (or deselect) it. When finished, type Shift+F8 again (or just move focus to some other window).
And yes, this particular keyboard interface is pretty wacked out. A more natural mechanism would be to have Ctrl+Arrow move the focus without changing the selection, then using Ctrl+Space to select (or deselect) the focus item. Thankfully, the list view control went for that approach rather than emulating the crazy Shift+F8 keyboard shortcut.