http://www.albawaba.com/news/watermelon-bomb-attack-israeli-bus-foiled-jerusalem
A bomb attack was foiled Friday afternoon in Jerusalem when an Egged bus driver discovered an explosive device packed in a watermelon while making a routine check as the bus was parked outside the Malkha shopping center in Jerusalem, said reports.
http://www.jta.org/1969/07/28/archive/boy-finds-explosive-at-circus-search-turns-up-more-averting-major-catastrophe
Benjamin Peretz and a youthful friend had been looking at the Tokyo Fair from the street but apparently did not intend to watch the performance. They wandered over to one of the numerous watermelon stands looking for spare melons. Benjamin opened a melon and observed a pencil-like object embedded in the opening. He removed it and playfully threw it at his friend. It exploded, injuring the boy slightly.
Police were called to the melon stand and began a search. They found the suspected melon and inside of it a kilogram of explosives. A second melon was found with three times that much explosive. An old coat, to which no one had paid any attention, was found to have 20 sticks of gelignite sewn into its lining. The circus performance was halted immediately and the audience followed instructions to leave by the tent through its back entrance while the search for more explosives continued. No more were found.
The police said that the pencil-like object was a timing device which had been set to detonate the explosives as the circus audience was leaving the performance. They said a major catastrophe in damages, injuries and death could have occurred.