Here's an idea for you james bond types with access to multimillion dollar manufacturing equipment.
If you've got the pillmaker equipment to make paintballs and can substitute the geletin for an inert oily substance that only breaks when launched at way over field legal force, you could fill them up with white phosphorus and load them into an automatic marker.
The target would be walking along when they hear this quiet "Fot, Fot, Fot!" noise and all of a sudden he and three of his mates are all holding their heads and covered with this stuff that just burns and burns and burns (on contact to air or water you have to pack the wound in mud to stop it), until the burning mess falls out their a$$es. If the theater of operations is a desert where there is no mud... well.
You could probably modify one of those AT85s from
http://www.adtacsys.com/index.shtml to mount under the barrel of an M-16... Hell, use it on its own. Some agencies already train with it. No muzzle flash. Flames hot enough to melt through car doors without a trail of flame leading back to the shooter. Flames only where you want them and to the degree that you want them. If there is already a DOD project on this anywhere in the world, I had the idea first back in 1990. I should have gone to work as a government researcher, if this wasn't my only crazy kill'em-all idea.
Only down side is the fact that if you get a ball breakage in the breech YOU are covered in this aweful stuff that just burns and burns and burns. But then you wanted to go and play with a flamethrower in the first place, and this is the safest, most tactically minded flamethrower I can think of.