The Moment

"The Moment" was something with which, or a time at which, the Doctor facilitated the end of the Last Great Time War. In or with "the Moment", the Doctor destroyed Gallifrey, the invading Dalek forces, the Time Lords, and all the horrific entities created during the Time War, as his initial method of foiling Rassilon and his plan to bring about the End of Time. (DW: The End of Time)

The Partisan confirmed to Rassilon and his council that the Doctor was in possession of "the Moment". (DW: The End of Time).

The Doctor would later state that all the combatants of the Time War had burned, "...wiped out in one second...". (DW: Dalek) This suggests the literal suddenness of "the Moment".

The Moment might have also been the modified De-mat Gun created by the Eighth Doctor, of which the Tenth Doctor said, "...once he turned the key in the lock, he doomed them all..." (IDW: The Forgotten) All this aside, there is nothing to indicate that The Moment was necessarily a piece of technology. Given the nature of the Time War, it could simply have been a literal moment — a period of

time, with a brief but indefinite length, within which the Doctor had the opportunity to do whatever he did to end the Last Great Time War. It is further possible that "the Moment" was a place that could be possessed, a key vantage point which gave him battlefield supremacy.

Potency

The Moment was a temporal super-weapon of mass-destruction and it may have been many things, The Hand of Omega (DW: Remembrance of the Daleks The Statue of Nemesis (DW: Silver Nemesis, The Key to Time (DW: Season 16, a De-Mat gun (IDW: The Forgotten or any number of those things. It was extremely powerful and had a nearly unlimited blast radius wiping out the Daleks and the Time Lords in the blink of an eye, burning them to a crisp. It was also the direct cause behind The Eighth Doctor's regeneration (DW: Last Great Time War. The Doctor activated the device from the so-called safety of the TARDIS but was caught off guard and caught in the blast radius being ripped to shreds and burnt to a crisp simultaneously by the force of the explosion, by the sheer gush of carnage. The TARDIS regenerated from the humble Gothic-esque abode it had been in the past to the corral desktop theme while The Doctor regenerated into his ninth incarnation. Basically he burnt with the Time Lords and the Daleks. He gave his life so all the billions of life-forms out there in the stars could go on living. His greatest sacrifice, his people, his home, even his own life was the greatest victory he would ever have in any of his lives.