I got a 6470 Lionel exploding boxcar at a bargain table with a complete mousetrap for $2.00. I always thought that Lionel really missed the mark on a potential separate sale item if they just done a very slight modification to the trigger that would allow the operator to blow up the car by bumping a train into it.

A 1/8" hole and a small length of bailing wire bent into the right shape was basically all it needed.
The wire can be turned and shoved all the way in with the cars safety pin in place to allow it to travel in a consist. I also added a little trough to hold fireworks poppers that go off as the mousetrap slaps down for an extra bang. You can see the car in action at the link below:

https://www.youtube.com/watch?v=6_wtO5J0OCY