Funny you mention it, Leprechaun, because I was thinking when I posted that making bongs and stuff illegal was kinda like giving a patent to the illegal business. Except when, unlike patents, enforcement favors the little guy.

The PTO used to adhere to uncoded standards of decorum, but now you can do nearly anything. I think you could probably only go for a design patent, in most cases. You couldn't argue a new use for smoking different substances, because they'd come back saying it's obvious you could smoke different stuff. The only utility-worthy idea I can think of, off-hand, would be a lowfire pipe or bong, based on the thermodynamic that a burning substance burns up some of it's effective ingredients, the lowest heat is more effective. I bet there are a few. I wonder how it plays out now in regard to patent law, given the obvious multi-purposes, as McGrath observed. But I'm too lazy to check into it.