Renault's F1 2.4L Formula 1 V-8
Following the Lego engine path, I was compelled to search for extraordinary revolutions per minute on YouTube. Although current Formula 1 engines are capped at 19,000 RPM, I figured 20,000 RPM would be about the limit for internal combustion engines.
Searching for 25,000 RPM didn't turn up much, but 30,000 RPM will lead to lots of on-board camera shots on RC cars.
40,000 RPM! That is where it starts to get interesting! A jet engine powered bilge pump! What a perfect companion for any campsite!
50,000 RPM! A 1960's Duetz jet engine running on diesel!
Searches of 200,000 RPM brought us to model jet engines. This specific engine's RPM is not mentioned, but it sure looks like an effective marshmallow toaster.