Plazma cutters are great, but they pop on rust and you still have to concern yourself more with fire. The old cut off 3" wheel is a favorite of mine as well. At .97 a piece for a good 3m wheel, they are very economical. And like 2bad said, they work great for knocking the top off of spot welds. Try putting 2 blades side by side on the mandrel, they last forever and won't dig in as bad when grinding welds.