Although Transformers are often rebuilt or otherwise brought back from apparent death, there are also many examples of them being partially reanimated as zombies, either self-aware or under the control of another.
While fleeing from Galvatron's Decepticons, Rodimus Prime and his Autobots find refuge inside an Autobot funeral barge, where Daniel Witwicky stumbled upon the reanimated form of Optimus Prime. Though most of the Autobots did not believe Daniel's story, Rodimus was obsessed with Optimus's memory, and tracked him down. After finding Optimus seemingly still alive, Rodimus happily handed over the Matrix of Leadership. However, things were not as they appeared, and Optimus immediately turned on them, left them to die in the funeral barge, and escaped in a ship he had built.
Upon Optimus' return to Cybertron, he claimed that Rodimus and his crew had died due to a cruel Quintesson trick, and commanded every single Autobot to help him strike back. This was just what the Quintessons had orchestrated from the beginning, having reanimated the Autobots' former leader solely for the purpose of leading the entire faction into a deadly trap. Now without the Matrix, Hot Rod and his crew had managed to escape, and Hot Rod battled Optimus one-on-one in an attempt to reclaim the Matrix and get to the bottom of this deception. The real Optimus eventually resurfaced, returned the Matrix to Rodimus, once again gave him his blessing, and the Autobots retreated. Optimus's final act would be to pilot their ship into the trap, detonating it, and leaving a nova behind... come back again later anyway.if he hadn't
After stealing dead bodies from medical universities, Dauros and Gilmer infused them with evil energy from Devil Z. These human zombies (in matching Decepticon jumpsuits) had begun to lay siege to a local city when Lander, who was nearby, changed into his Pretender form and battled them. However, the zombies began to disappear in a flash of light after they had run out of energy.
The Decepticons realized that they needed to infuse life energy from living humans into the zombies to avoid this problem. After kidnapping several human boys, the Autobot Pretenders came to the rescue and befriended one of the boys, Cab, who joined their team.
Marvel Comics continuity
In a desperate bid to stop Grimlock from exploding the walking bomb Guardian, Wheeljack radio-controlled the body of Optimus Prime (Shockwave had the head), to grab Grimlock's arm. Without a brain module to control its functions Prime's hand could not let go of Grimlock's arm. This resulted in Grimlock's hand being ripped off when he was knocked away from Prime by the Guardian robot.
Several years later Ultra Magnus and the Sparkler Mini-Bots encountered similar technology used on a much broader scale. Traveling via dimensional portal to the new home of Emirate Xaaron's resistance movement in Kalis, they arrived to find the place vacant and ransacked by beings unknown. After capturing the Decepticon Flywheels in Tyrest and bringing him back into Kalis, their captive shook with fear. The dead walk in Kalis!, he warned, as the fists of the unliving punched up through the ground beneath them.
Though Ultra Magnus refused to return Flywheels's gun to him, the Decepticon helped Magnus and the Sparklers beat back the undead hordes. Their attempts, however, seemed futile -- no matter how hard their attackers were damaged, they still functioned! Finally, Flywheels and the Sparklers reverted to vehicle mode, where they could use their weapons to destroy the zombies more effectively. But alas, Magnus was stunned to realize that the beings they put down were formerly Autobots. Realizing that the zombies were being animated by remote using a radio signal, they travelled ten kliks outside Kalis to the Baird Beaming Transmitter. The signal was indeed shut down, and Magnus discovered that the signal was coming from deep within Cybertron...
The zombies were actually activated by the mad Autobot scientist Flame and sent to stalk the area surrounding Kalis to scare off intruders, while he set into motion his doomed plan to transform Cybertron into a spacefaring battlestation. Though he captured his rival Emirate Xaaron and other inhabitants of Autobase, he would have been easily thwarted -- if not for his zombification of the late Wreckers leader, Impactor. The current Wreckers leader, Springer, was shocked into inaction at the sight of his former leader, and if it weren't for Impactor's mind reasserting itself, the planet would have been lost. Impactor once again sacrificed his life to save the others, staying behind to deactivate Flame's mechanism as it annihilated him.
Later, Dreadwind and Darkwing were sent by Megatron to reclaim Starscream's charred corpse on Earth. Starscream's remains were possessed by the essence of the Underbase and went on an insane rampage, nearly killing Dr. Susan Hoffman and her assistants. After Starscream was diverted away from the humans by Backstreet, Dogfight, and Override, the trio of Triggerbots tried in vain to stop the rampaging zombie. Eventually, the Underbase realized it was acting insane and regained control, but as soon as it did, Dreadwind and Darkwing siphoned all the power out of it, and Starscream's corpse returned to being an inanimate pile of scrap, which the pair quickly collected.
Meanwhile, Ratchet had been working long hours to repair the Autobots' massive number of casualties from the Underbase Saga -- so long, that he began to hallucinate, seeing his patients rise up from their repair beds and blame him for their condition. Megatron, to whom the corpse of Starscream was being delivered, required Ratchet to repair him, so the former Decepticon leader sent the Micromaster Sports Car Patrol to trick Ratchet into returning with them to Cybertron. To do this, Blackjack and his fellow Micromasters made Ratchet's hallucination real, animating Ratchet's patients. However, this began to backfire when Ratchet decided to give himself up to his accusers. The Sports Car Patrol decided this wasn't the best course of action and tried to lure him back with a different plan.
While looking for clues to the identity of Playback's killer, Nightbeat suddenly found himself, Siren, and Hosehead under attack by the prime suspect -- Thunderwing! Ultimately, Nightbeat was able to save their lives by having his Headmaster partner, Muzzle, become the head of Playback's corpse, momentarily distracting Thunderwing with its scary zombieness. As soon as Muzzle jumped clear, the trio of Autobots fired at the corpse's fuel supply, causing a huge explosion which forced Thunderwing into retreat.
IDW comics continuity
Kup had been marooned on a distant planet for quite some time when They started coming for him. They only came at night, when the suns would stop filtering through the planet's beautiful, indigenous crystals, creating such beautiful music... Kup could not allow Them to take the music away from him, and even though his buddy Outback, the only other survivor of Kup's crew, refused to help him, Kup was able to beat back every single last one of Them every single night when they'd come for him.
What Kup didn't know is that They were not zombies, but Autobots sent in to rescue him. The antique anti-rad armor they wore to protect themselves from the extreme radiation caused by the crystals also disguised their identities to Kup, who was suffering hallucinations at the hand of the radiation. Oops.
Beast Wars Metals manga
As Optimus Primal's corpse floated in Earth's orbit following his sacrifice at the hands of the aliens' Planet Buster, Predacon Megatron realized true strength was not only in numbers (fashioning himself an army of drones), but also in retrieving Primal's remains, reassembling it, and reanimating it as a zombie. Upon initial activation, the zombie asserted its dominance over Megatron's new army of drones.
Thankfully, before Megatron and Tarantulas could make the process permanent, the Maximals showed up and Rhinox injected Primal's Spark (which he had retrieved from Transwarp space) into his old body. Thus ended the short career of Zombie Convoy.
Beast Wars Neo
After the defeat of Megatron and the Maximals' takeover of the Grand Mal, Silverbolt and Blackarachnia were investigating the fields of sparkless Transformer bodies when they were attacked by a zombie-like creature. A seemingly-invincible corpse battled them. Blackarachnia attempted to use her energo-web attacks, but it merely absorbed them, until finally, after Blackarachnia threw another corpse's power core at it, the zombie collapsed. A mysterious energy ball lifted from the zombie, and it disappeared through a grate in the ground.
The energy ball appeared next in the technorganic orchard that Rattrap and Botanica were tending, bringing life to a deactivated Motorcycle Drone. Botanica attempted to use her energy weapon powers against it, but like Blackarachnia's energo-webs, it merely absorbed her attack. After being expelled too from this body, it fled to the surface into a deactivated Aero Drone, where it attacked Cheetor, Obsidian, and Strika. Nightscream tried a different approach of "draining" the creature of its power, but it drained Nightscream's own power from him. The Maximals began to see a pattern in the zombies' attacks, and regrouped inside the Grand Mal, which seemed to be its target. Finally, Rattrap had an epiphany, realized what was going on, and captured the energy ball inside a diagnostic drone. The energy ball was actually the polarized Spark of Megatron. Surprise!
Despite Unicron's apparent death inside the Unicron Singularity, his essence's will was still strong enough to use the reality-altering black hole to bring the Terrorcon Scorponok to Cybertron. Now Dark Scorponok, this undead creature stalked the evacuated planet surface, screaming in hunger and pain, crying out for Sparks upon which to feast. At first Dark Scorponok assaulted Skyfall, who survived due to his powerful forcefield ability, but the monster was drawn away by Ramjet's evil Mini-Con minions, towards the Primary Energon Reserves Control, where Vector Prime and Sentinel Maximus were located. After a prolonged fight, Sentinel Maximus was able to defeat Dark Scorponok, after which he and Vector Prime realized this was just a diversion. Leaving what was left of Dark Scorponok, unable to solve his affliction, their attentions were needed elsewhere, below the planet's surface.
Immediately after Megatron's death, Starscream appointed himself the commander of the Decepticons... who were all dead. Noticing the mechanical devices that the All Spark had animated, Starscream tore the solidified All Spark energy from them and used it to turn the Decepticon corpses into undead soldiers. Without any mental functions whatsoever, they simply walked forward and attempted to kill, and very nearly tore apart the weakened Autobots before Ratchet worked out how to stop them.
Space barnacles are parasitic life-forms that can be considered "zombie-inducing" in their quest for energy. Some of them attached themselves to the dead body of Megatron and managed to reanimate it, evolving themselves into semi-awareness and later absorbing other machines. In this state, they shared with zombies the property to "infect" other robots by simple contact, turning them also into mindless drones, ready to spread the infection. ("Normal" space barnacles simply drain energy, but presumably do not take over Transformer minds.) Prowl and Bumblebee were finally cured from their contact with the creature when Sari blasted the space barnacles off with hot water.
- Jetfire, while he was an animated unliving Transformer controlled by Shockwave and later Buster, was not strictly a Zombie. He was not given life until after he was used as a mindless puppet by diabolical masters.
- Metrotitan is not a reanimated Metroplex as was commonly believed for some time.
- Dinobot II, though he looked like an undead Dinobot I, was more of a Frankenstein's Monster than a zombie.
- Primeval Dawn's "Zombie Tarantulas," as referred to by some fans, did inhabit the reconfigured remains of his previous body. This seemed to be a full return to life, despite his new black and gray color scheme, rather than being undead.
- Energon Starscream, though brought back from the dead, was more ghosty than zombie-y. Even Aaron Archer referred to him as an "Energon ghost."
- Dark Crumplezone, though he was also brought back from the dead, likewise wasn't very zombie-y; indeed, he even came back smarter (according to his on-package bio) and with his personality intact.