As a lighting designer, I use
vectorworks spotlight. AutoCAD is a little to powerful for what I need, plus I have to boot my computer into the PC side, which I hate doing (even though I need to for hogPC, ah well).
WYSIWYG is a cool previz tool, but I've never felt the need to use it. Using VW I am able to hang a light 20 feet off the ground, focus it to focus point A, and see what my beam-spread will be. I've never bothered to learn how to render in VW, and again, I've never felt the need to.
So, yea, Vectorworks is my tool of choice.