The intermittent, low-draw tools like the aforementioned brad nailers work pretty well. But an air-motor tool, like a die grinder or cutoff wheel, needs a huge amount of air. I ran one at a junkyard once, using an old Max Flow and a 20-pound CO2 tank. In a relatively short period of time (a couple minutes, max) I'd nearly frozen the tank.
As I recall, I think I used about a third of the tank- or rather, what was in the tank, since it wasn't 100% full when I started.