Megatron and Starsceam's fight in issue 6, which the whole series has been building up to. Even with Starscream's Ore-13 enhanced prowess, Megatron is barely scratched, and he quickly blasts a hole in Starscream's torso.
Before that, his threat to the rogue infiltration unit.
Megatron: You will stand down. If you fight, you die. Ultimately, there is no room for mercy. In the end, you are all expendable. Choose.
The moment the Wreckers are introduced, being fired on from all sides while trying to get into a reinforced bunker (and having difficulty with the local terrain). And then there's Springer being bothered on the phone.
Springer: "Lost cause"? What do you mean "it's a lost cause"? Of course it's a lost cause! That's why we're here!
Optimus finally putting Thunderwing down for good, with an epic speech to match.
Roller making his first appearance by taking out Blitzwing in one shot. And Blitzwing was camouflaged at the time.
Optimus's first shot in his fight with Megatron manages to take out Meg's arm cannon. Megatron swiftly proves he doesn't really need it.
Hardhead's reaction to Nightbeat's Manchurian Agent programming going off. He just calmly, and casually, shoots him through the head.
Also, when he interrupts Jhiaxus' Evil Gloating and gets shot point-blank in the head. It doesn't do anything.
One for Hot Rod, who has been tormented for years by the slaughter of his team while obtaining the Magnificence, a font of infinite knowledge. He does not know that his team was betrayed by Dealer, a Decepticon mole. Dealer finally finds a way to convince Hot Rod to lead him to the Magnificence, with himself in tow. As they approach it, Hot Rod wonders aloud how the Decepticons intercepted his team, how their mission was sabotaged, and why Dealer was captured but the others were killed. His first question to the omniscient 8-ball of the stars? "Did Dealer betray us?" "Yes!" Cue Hot Rod shooting Dealer off the mountain.
Even better, Dealer was already drawing a gun on him. Hot Rod's too quick for him.
Spotlight Shockwave. Shockwave is very much Awesome by Analysis but here he takes it to the top, seeds other worlds, prepares them for natural energon creation, then the Dinobots come in and unleash hell, and for a moment it seems they have one finishing him off with missiles and setting him ablaze. Until... Out of the Inferno comes a enraged Shockwave, and the collective look on all of them says that they know they are screwed. They are.
Grimlock takes the moment back from Shockwave by pre-emptively setting his ship to shoot at a nearby volcano, causing the magma to overtake the field, sealing Shockwave within the cooled magma just to make sure he couldn't escape.
Spotlight Hot Rod: Hot Rod manages to infiltrate the most heavily secured prison the Decepticons have, on his own. And he starts by surfing in on a meteor.
Out-of-universe, Spotlight Wheelie manages to do the impossible. Takes a character widely considered The Scrappy and makes him interesting. It works.