Sorry I didn’t answer this sooner! I meant to and got sidetracked with some color stuff… 
What I use depends on my mood mostly. If I’m in a rush and need something straightforward and fast I’ll use reveal.js (or throw something together on http://slides.com/).
I was using Sozi occasionally but have not in a while. However, I will often just drop into Inkscape if I want to play around a bit - particularly with typography, images, etc.
Now I’ll have to go and play with Pandoc again…
I like the idea of using a “starter” slide deck, and something like Pandoc would be great for that. I just know that folks often like to personalize their slides for their own style and tastes.
I’d personally say that assets + styleguides might be really useful too. This is a matter of taste again, of course.