Well, my latest idea is an exploding Russian anti tank dog. For those who don't know what that is, see here: http://en.wikipedia.org/wiki/Anti-tank_dog They weren't very effective but they were used and did destroy and damage many german tanks.
I was in Hallmark today and noticed a recordable birthday card and the idea sprung to mind. The card can have a 10 second message recorded on a small device inside. When the card is opened, the message plays, eg 'happy birthday daddy' from his little girl etc.
So my idea is to use a modified GI Joe shepherd (has to be reworked into almost a lying position and put a little backpack on it with a stick, sticking up, just like the dogs had.
Then, take the recording device out of the birthday card, record the sound of an explosion on it and glue it under a 1/18 german tank, with the end that activates the sound hanging down.
Now i can either push my little dog under the german tank, or have the tank drive over top of the dog, either way the dog will push against the little end of the device that is hanging down under the tank, that activate the sound. Once it pushes it far enough the explosion sound will play. Boom! It's pretty loud.
And that's it, simple and simply fun.

Note: no animals were hurt in the making of this toy.