Transformers: Energon Wars
Set in the near future (say the mid-21st Century), Earth is more or less at peace; the Autobots have driven the Deceptacons from Earth and Megatron is dead, his corpse buried in an unassuming tomb of concrete. What Decepticons remain are a rag-tag gang of raiders and scavengers, picking at Earth's weakest points but unable to gain any ground. The Autobots remain strong thanks to their human allies and the Matrix of Leadership, which is capable of giving sentient life to Earth's technology.
A human/Autobot research group, Project Rollout, has studied Autobot physiology, giving them insights into robotics. Weapons, armor, even vehicles are being created that have the capacity to transform (though they lack sentience of their own). Humans can now enclose themselves in transforming vehicles, which become Deceptacon-sized battle suits capable of fighting Transformers at their own level.
All seems well... until Starscream leads a sudden attack on Project Rollout's HQ. Wielding what he calls the Decepticon Matrix of Conquest, he releases its power into the base - granting the Decepticon's evil sentience to the base's machinery.
The game begins with you, an unnamed human who volunteered for weapons tests. Your name and backstory classified, as you were an Omega-Black level volunteer. After testing some of the game's weapons and vehicles in the Tutorial section the attack by Starscream begins. As the human researchers are mostly slaughtered and the Autobots are busy fighting off the new Decepticons, Optimus Prime is able to save you from your own weapon by energizing them with the Matrix of Leadership. The weapon gains a sentience of its own, but he mix of Autobot/Deepticon energies in it make it both eager to fight yet not hostile to you. While the Autobots fight the Decepticons you fight your way out of the base, saving as many humans as you can.
In the meantime, Starscream release the Decepticon Matrix's energies across the nearby city, creating a war zone and inadvertantly re-awakening Megatron, who claws his way free and claims the Matrix of Conquest for himself. Megatron plans to use Project Rollout's Energon Generator (a perpetual energy device that was to end Earth and the Autobot's never-ending search for Energon) to fuel the Matrix of Conquest, it is up to you to take the war to the Decepticons and prevent Earth's technology - all of it - from being formed into a Decepticon army powerful enough to conquer Earth and the galaxy.
Gameplay
The majority of the game is played as a human-sized FPS'er. Your transformable gun can take the form of any weapon it scans, and can be upgraded by absorbing certain parts, allowing you a large inventory of weapons to battle Decepticons of every shape and size.
Certain sections allow you to board one of Project Rollout's un-Decepticon-ized transformable vehicles, making for some high-speed vehicle sections both on the ground and in the air, which can shift to over-the-shoulder close-range Transformer-sized battles as you engage gigantic robots on their own level in a mix of shooting and melee battles. Unlike Michael Bay's noisy looking bots, Energon Wars depicts the Transformers as being more like those seen in Real Steel, clearly robotic and believable, but also easier to make out in the middle of a brawl. Heads and limbs can be torn free to dispatch your enemies, with a variety of brutal finishing moves and destructable environments to give the battles a visceral feel.
Multiplayer would have two types: Human and Transformer-sized Battles. Players can customize both Autobot and a Decepticon teams. Both have pure Transformers (that is, normal sized Transformers and human-sized Transformers) to pick form, but Autobots also have armored Project Rollout humans who can engage in Transformer-sized battles using Rollout suits.
You get a full run of FPS multiplayer. Capture the Flag, Capture Territory, Team Deathmatch, etc. Certain battles are All Human-sized or All-Transformer-sized, but some battles can be organized so players can get in and out of Transforming vehicles, allowing for a blend of both (like Battlefield, only with rock 'em sock 'em robot mechs).