How to assign tilde to command-tab?
You can do this with Karabiner with a private.xml such as this:

&lt;?xml version="1.0"?&gt;
&lt;root&gt;
  &lt;item&gt;
    &lt;name&gt;~ to ⌘⇥&lt;/name&gt;
    &lt;identifier&gt;private.tildetocommandtab&lt;/identifier&gt;
    &lt;autogen&gt;
      __KeyToKey__
      KeyCode::BACKQUOTE, VK_SHIFT | ModifierFlag::NONE,
      KeyCode::TAB | ModifierFlag::COMMAND_L
    &lt;/autogen&gt;
  &lt;/item&gt;
&lt;/root&gt;


This will effectively replace command with shift and tab with tilde, so that holding shift and pressing tilde twice will switch to the third app rather than back to the first.