Quantum Torpedo

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Background
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Because Photon torpedoes use a mixed matter/anti-matter reaction as their warhead they are highly unstable. Anti-matter is very unstable and must be kept in a magnetically sealed container. You often hear in a battle situation, that before torpedoes are launched, the weapons officer has to arm them. Armed meaning that the torpedoes must be filled with anti-matter before they can be fired. This process is relatively fast, a matter of seconds, but seconds can be a bad thing when in battle. A malfunction in the arming mechanism can ignite the anti-matter and blow a hole in the hull of the starship. For this reason the Starfleet weapon designers came up with the quantum torpedo.
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Details
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Designers had to find a power source for the warhead that was stable and powerful. Something that could be loaded into a torpedo when their made and remain stable throughout a mission. The designers found such a power source in the form of the Quantum Filament. You will recall that the Quantum Filament is a natural form of energy in space. It has no mass and if triggered just right can release almost astronomic amounts of energy. Using reading taken by science teams studying natural filaments, the designers created small artificial filaments. What makes a Quantum torpedo so powerful is that the warhead contains 50-100 small artificial filaments. These can be loaded into a torpedo before they are put on a starship, and remain stable. The filaments can then be made active by a cascade reaction activated when the torpedo is launched from a starship. Up on impact the filaments spread out and explode, ripping any starship hull apart.

Overall the Quantum Torpedo is one of the major advances in weapons technology for over 100 years and has aided in keeping both the Borg and Dominion at bay since its inception.