Chocolate
Anything that when it reacts explodes when not stabilized, so for example water and potassium.
A Canister of o2, a canister of heated plasma, and a tank transfer valve. When you put the o2 into the canister of hot plasma it should cause a fire in the canister and blow up.
By activating a mousetrap in hand and then adding it to the bomb, when someone tries to interact with the bomb by clicking it or opening up where it is stored it will cause it to activate.