If you are looking for a good souvenir to take home when you visit Washington DC, I highly recommend getting some large coins from the street vendors.
They are about $3 each (you might be able to talk them down a little, but not much). Oster has used them to sort coins.
And we use them to play "hide the quarter". Have you ever played "hide the quarter"? Basically, one person hides the coin in plain site and then everyone else tries to find it.