Missing from the list? The S5-based slide-show tools that are part of docutils.
The only issue with S5 is that you need to carefully review each and every page to be sure you material fits. There's no autosizing of the fonts, or other trickery to pack too much trash onto a slide.
TIL that Lync/Skype doesn't politely handle Keynote on a Mac. You must mirror displays because Lync can only share one of your displays, and it's not the one Keynote chooses to display on.
I often use Keynote because it's expedient. I sometimes use S5 to show off an entirely open-source toolchain.