Exploding Lionel Boxcar
Lionel is famous for having popularized model trains. While they sometimes took liberties with detail and scale, this let them bring a lot of fun toylike accessories to your train layout. Lionel's fame still lies in their large O scale fleet, but they also produced trains in the popular HO scale from 1957 to 67.
Most of Lionel's most famous rolling stock did things. There is the famous aquarium car, a livestock loader that uses loud vibrations to rattle the cattle into place, as well as military cars with spotlights and launching missiles. They brought some of these "Operating Cars" to HO when they tried to break into that growing market.
The mechanism in use on the HO exploding box car above is rather clever. It's a spring mousetrap affair that you set before carefully assembling the sides and roof. The car stays together as it's trundling down the pike thanks to a catch, but unlock that and a protrusion on the bottom becomes the freight car's glass jaw. Hit the right stretch of track and SNAP! The boxcar (marked for carrying explosives, hah hah...) flies to pieces.
Maybe it's not cool to play at blowing stuff up these days, but this is still a pretty nifty toy. Even after 50 years the spring is still very snappy and sends the car to kingdom come. Maybe I should repaint it to look like the boxcar is carrying cheese, so that maybe I can catch a mouse inside.