A well hard bit of ordinance dreamt up by the Czechs...the people who gave us Skoda's (Can you believe it?).
As little as 250g can down an airliner. Around 10 tonnes (40 000 airliner worths) of Semtex is produced annually ... jeez that would be a big bang! See the climax of V for Vendetta for the perfect place to try this out.