The gun amnesty that's running before the new firearms laws come in has netted a few interesting items:

A used LAW rocket launcher.
A shoulder mounted RPG launcher.
A fully operational AK47 assault rifle, probably a souvenir from Desert Storm.
A home-made cannon(!) painted in camouflage colours and able to fire a two and a half inch cannon ball.

I'd love to hear the story behind the last one...