AllSpark

The AllSpark is an ancient source of energon and power. It is pure energy and the source of all life on Cybertron.

Transformers: Exodus
The AllSpark resided in the Well of All Sparks on Cybertron, where it carried out the will of Primus by creating every Cybertronian life. When the Great War erupted, however, the AllSpark briefly ceased to produce life in a seeming act of divine rebellion, only to apparently change its mind and create one final generation — including Bumblebee—who entirely joined the Autobots. As the Decepticons besieged Iacon, Optimus Prime made the decision to eject the AllSpark into space.

Many cycles later, after the war had drained Cybertron of energon, forcing the Autobots and the Decepticons to depart the planet, the Ark emerged from the space bridge to an unknown spiral galaxy, and detected the energy of the AllSpark nearby.

Transformers: Prime
The AllSpark was the very heart of Primus himself. During the Great War, Optimus devised a plan to move it away from Megatron. Alpha Trion forged an invincible container to hold its immense power. It was sent to Theta Scorpii as the sector was hazardous to anything that lived.

When the war ended, Optimus and Wheeljack retrieved it. While they were on route back to Cybertron, they learned that Unicron had returned. Unicron went for the AllSpark to destroy it when they returned, but was blocked by Optimus. In fear of Unicron devouring the Allspark, Optimus released its energy into the Matrix of Leadership, making it both the Allspark and the former at the same time.

Optimus flew away from Unicron to reach the Well of Allsparks, but was shot down by Unicron and had the "Allspark" snatched from him. Unicron opened the vessel that once held the Allspark and, just before realizing it was a trick, Unicron's Anti-Spark was sucked into the vessel, tearing his pure energy form from Megatron's body, trapping him forever.

Optimus told his team that he must go into the Core in order for life on Cybertron to exist again. Bumblebee promised Optimus that they (Team Prime) will keep the peace in his name. Optimus smiled at them and flew into the Core, becoming one with Primus. Millions of Sparks fly into the sky, and one red spark, possibly Optimus, shines out.

Transformers: Robots in Disguise
Upon his return to Earth, the evil Megatronus tried to execute his doomsday plot of using his spark fuser to combine the Anti-Spark of Unicron from Earth's core with the AllSpark from Cybertron in order to destroy both planets. He activated his staff, causing a portal to open in the sky and the AllSpark to come through, but Optimus managed to shatter the fuser, sending both AllSpark and Anti-Spark back to their resting places and ruining Megatronus's plan.

Transformers: Universe
The AllSpark was the very heart of Primus himself. It resided in the Well of All Sparks on Cybertron, where it carried out the will of Primus by creating every Cybertronian life.

Trivia

 * Normally Ratchet is the one who mentions the AllSpark, as he says, "By the AllSpark!"
 * Wheeljack hoped the AllSpark was bigger than he had imagine. Looks like a Transformer live action movie reference.
 * Usually when someone says that someone has become "one with the AllSpark", they mean they have died and is in a heaven like universe.
 * The Allspark can sometimes glitch and affect the personality of a Cybertronian, with Knock Out being an example