[mindslight]

If you're just talking about when something in a feedback loop gets disconnected (causing the output of the error amplifier to go to an extreme), you can do this with cruise control and a manual transmission (at least on some cars). Engage cruise control on the highway, then pop the car out of gear without using the clutch (so cruise control doesn't disengage). As the car's speed drops, the cruise control applies ever more throttle making the RPM shoot up. I've also done this going downhill with the car naturally gaining speed (and RPM going to idle).

[bewaretheirs]

Huh. I've owned a few manual-transmission cars over the years and they all disallowed this trick -- pressing the clutch would disengage cruise control just like a tap on the brakes.

[mindslight]

Yeah, pressing the clutch will do that. But you can pop the car out of gear without pressing the clutch. (IIUC) the synchros provide some positive holding force that holds the transmission in gear, but you can overcome it. Also that force goes down with the amount of torque being transferred through the transmission, so you can make it easier by playing with the gas pedal a bit.