Ral, I'm gonna disagree. I have some heavy scissors- I think they're called "Ultimate Shears", made by Farberware- they work great for cutting cardstock. I've tried exactos and razors, too, but with them you can't go from slice to slice easily.
And to the ruler-lovers.. if you can't cut a straight line with a printed guide, wtf?
Also, most people resin and bondo anyways, so those nice, straight lines- they're going to be pointless when you smear them with mud and sand it down.
I'll also say that scoring is the fastest way to fold. Forget aligning your ruler, tracing the lines with a colored pen, etc- cut to the chase and score the cardstock directly. From there, folding is very, very easy.