One little known variant of the 727 - the JATO option.
Apparently a Mexican airline wanted to be able to operate fully loaded out of Mexico City on a hot day, and the JT8D wasn't quite up to the task. So they added JATO bottles - if they lost an engine after V1, they hit a switch that fired a couple of JATO bottles (I think they were located in the wheel wells?).
According to a coworker that had been on board for the flight tests, you couldn't really tell the difference when they fired the JATOs...
Eventually they were able to upgrade the engines sufficiently that the JATO option was no longer needed. From what I heard they were never actually used in anger.