These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Big Lipped Alligator Moment: The Lever Transformer that appears during Jazz's chapter. You attempt to use a lever, it transforms into a robot that dances around for a minute, a door behind it (containing a lot of Energon shards) blows up, and it transforms back into a lever.
Demonic Spiders: Shotgunners. Fast, heavily armored, and more than capable of getting up in your face and executing you with a point-blank shotgun blast before you even know what hit you.
And that's to say nothing of the Guardians in Cliffjumper and Starscream's levels. Identifiable by their gray plating and green lights, they rove about looking for an enemy to blast. The best way to kill them is to cloak (there's a reason they only appear when you're playing a character with that ability) and sneak up behind them, then perform a quick execution attack. But if you draw their ire, then welcome to die. They transform and pummel you with a brutal series of blasts more than capable of smashing your shields before you even know what's happening, and even if you re-cloak, it becomes very difficult to get them to go back to their docile form. They're killable, but it's an endeavor. Taking on one is antsy but doable, but taking on a squadron of them is suicide, full stop. And yes, they will chase you into different rooms. Thankfully, they can't follow Cliffjumper into the vents nor can they follow Starscream if he flies off.
Even Better Sequel: It takes everything that worked in War for Cybertron and refines it into a more narrowly focused thrill ride that puts you into some amazing set pieces. While War had a decent story, the co-op campaign forced them to generic-ize the characters and their abilities. This game actually puts you the the controls of a specific character and you get some very dynamic experiences because of it.
Fan Favorite: Metroplex was able to pull this off due to being a giant One-Man Army and crushing Megatron. Grimlock was practically designed to be this with, being every bit as much a badass in the game as the lead planned for him to be.
Game Breaker: The Thermo Rocket Cannon with its firepower and lock-on/homing abilities, so much so that the first patches to the game nerfed it.
Genius Bonus: The Earth in the holograms does not show a contemporary Earth. It's in the process of forming individual continents as Earth really was at the time of the dinosaurs.
Let's be honest: you'll be stuck with an expression of awe for about half of the game. What happens is simply epic.
It's the Same, so It Sucks: Not in the sense that it's like War For Cybertron, but like the video game tie-in of Dark of the Moon, which had single-player levels that "focused" on making the playable Transformers unique. Hopefully, High Moon will manage to cure this problem.
To note, it was the removal of co-op that got to most people.
Although some folks changed their tune when they learned that said tie-ins would result in the Dinobots appearing in Prime.
Memetic Mutation: "METROPLEX HEEDS THE CALL OF THE LAST PRIME" and variations of it have become popular with Transfans.
Moral Event Horizon: When Optimus sees that Megatron is as desperate for energon as the Autobots, he proposes a truce to resolve their mutual problem. Megatron refuses, blames Optimus for everything, and insists that he alone is Cybertron's future, swearing to kill Optimus and the Autobots.
Shockwave's experiments cross this, as he surgically rips apart and rebuilds whoever he experiments on. To make it worse, he keeps them functional and aware while he tears them apart and rebuilds them. While most of the Dinobots seemingly don't remember, Grimlock does.
Most Annoying Sound: "Hurry Grimlock, Snarl can't take much more of this!" It wouldn't be so bad if not for the fact that he says that almost every, singe, time, Snarl loses health. Also, Sharpshot's taunts whenever Grimlock takes damage, which is likely intentional.