Remap Space and Command
Install Karabiner.
Place this in your private.xml (~/Library/Application Support/Karabiner)

&lt;item&gt;
        &lt;name&gt;Use Space as Command modifier&lt;/name&gt;
        &lt;identifier&gt;private.space_command_key&lt;/identifier&gt;
        &lt;autogen&gt;__KeyOverlaidModifier__ KeyCode::SPACE, KeyCode::COMMAND_L, KeyCode::SPACE&lt;/autogen&gt;
&lt;/item&gt; 


It goes in between the &lt;root&gt; and &lt;/root&gt; tags.

If you want to remap it to Control instead, you can change the KeyCode::COMMAND_L to KeyCode::CONTROL_L.
Launch Karabiner, press ⟳ ReloadXML, and check the box