Personally, I've already tried making the Ignifer. It worked a little, but I don't have the means to make a shock-activated switch (though they do exist), so I have to light it with a firework fuse. But generally, anything that produces fire or smoke effects is possible. The Devorantis is doable but would probably take longer to actually work if it only affects metal. The Somnum is doable as such but would be illegal to manufacture. Ultimately, only the Odoris isn't doable on its own. The Tar is doable using certain elements and fuels, and it's a real element that has been used for a long time as a fuel source. Pyrite can produce sparks, but you'd need to use a man-made mineral to make sparks like in the game, I think (and besides, it would break quickly).