I think flame throwers would be very effective in the urban fighting we do now in the ME. Something to bring back.
The USMC requested them in the Battle of Fallujah, but were rebuffed.
They made do with what they could, and in one encounter where the Iraqis had turned a concrete house into a pillbox, and multiple Marines were killed or wounded there, they shot holes in a tank of cooking or heating fuel on top of the house, let it drain into the house, then set it afire and listened impassively (and with some satisfaction because of their dead buddies) as the terrorists inside screamed and were consumed.