When the Transformers' war moved to Earth in 1984, current Decepticon leader Shockwave elected to increase his forces by creating new Transformers with the power of the Creation Matrix. Capturing the Autobots and decapitating Optimus Prime, Shockwave tapped the energies of the Matrix and brought the Constructicons to life. -"The Next Best Thing to Being There!"
Once there, both sides battled the creature the Matrix had created, which had grown to enormous size, with Thunderwing ultimately killing the beast and taking the Matrix.- "Dark Creation"
The Decepticon immediately attacked the spaceborne Ark, manifesting the Matrix power in the form of a giant, vaguely humanoid energy field around himself. Soon, however, the Matrix began to speak through Thunderwing, delighting in the firsthand experience of evil, and the Decepticon realized he was being possessed. Thunderwing tried to mentally battle the Matrix, to no avail, but the Autobots exploited his erratic behaviour to impale him with a harpoon and blow him out the Ark's airlock into space. -"All Fall Down"
The terrified Galvatron instructed Scourge to dispose of the Matrix, but Scourge grasped the true nature of its power where his leader could not, and instead placed it within his own chest. The Matrix's energies warped his body into a powerful, misshapen hulk, increasing his power to the point that he was able to oust Galvatron and take control of the Decepticons himself. Scourge proceeded to lead the Decepticons in an attack on Earth, only to be bested by Hot Rod, who had since learned the importance of "the burden hardest to bear", and reclaimed the Matrix once more. -"The Burden Hardest to Bear"
Dreamwave G1 Comics:
When the Autobots and Decepticons were finally able to return to Cybertron, a chain of events ultimately led Optimus Prime into a confrontation with Shockwave in Vector Sigma's chamber. Knocking Prime out and blasting his chest open, Shockwave harnessed the energy of the Matrix and used it to access Vector Sigma's databanks in an attempt to learn all of the dark secrets at the heart of Cybertron. -"Countdown to Extinction"
There's a few more examples at the Transformers wiki http://tfwiki.net/wiki/Matrix_of_Leadership