
Grenade
Dangerous Object
A grenade is a weapon, so using it in similes implies something dangerous or harmful.
His sudden resignation was a grenade in the company's stability.
Immediate Action
Speaking about grenades usually means quick action is needed because of the immediate danger they present.
Drop the grenade and run to safety!
Not a Toy
Grenades are serious and deadly weapons; they should be spoken about with caution and respect.
He learned about the severity of war when he saw a grenade explode.