Ctrl+P – When presenting, Ctrl+P will turn on the pen tool so you can draw on your slide. In edit mode, it launches the print dialog. You will be able to save your drawing as you exit show mode.
Ctrl+H – In presentation mode, Ctrl+H will hide the pointer icon. In edit mode, it will launch the find/replace dialog.
Ctrl+A – When presenting, Ctrl+A will reveal the pointer icon, if it has been hidden or changed. In edit mode on a slide, it selects all objects. In the navigation pane, it selects all slides.