Check out US Patent #6055910
It is for a toy gas fired missile and launch assembly. Not interested yet? Maybe when you see where they collect the “gas” needed for this!
C. Means to feed a combustible gas mixture into said chamber, including an intake tube communicating with said chamber and having a normally-closed valve and an inlet to the tube, the inlet of the intake tube being placeable adjacent an anal region of the operator from which colonic gas is emitted whereby when the piston is pulled out the resultant negative pressure acts to inhale the colonic gas into said chamber to produce the combustible gas mixture;