The Decepticons escape Autobot City riding inside of Astrotrain, and the massive space-shuttle begins to shake, telling the survivors "Jettison some weight or I won't make it back to Cybertron!!" Starscream, being Starscream, of course took this chance:
Starscream: Fellow Decepticons, Astrotrain has proposed that we "lighten our burden."
Bonecrusher: In that case I say it is survival of the fittest!!
Then the little-bastard proposes that he should be Decepticon leader. The Constructicons protest, saying that they transform into Devastator, the biggest Decepticon of all. Soundwave protests against both of them, in a rare instance of him showing a sense of humour.
The whole sequence is even funnier if you know that, according to Word of God, Starscream won leadership by standing in the far side of Astrotrain while everyone else was fighting and then clocking the guy who actually won the fight.
At Starscream's coronation:
Astrotrain:*just about to put the crown on Starscream's head*
Constructicons: *playing trumpets*
Starscream:Get on with the ceremony!
Astrotrain:*tries to put the crown on Starscream again*
Constructicons: *interrupts with trumpets again*
Starscream: *shoots the trumpets*
And then Ramjet points his guns at the Constructicons just to be sure they won't interrupt again.
Unicron gets one, in a surprisingly sarcastic moment;
Megatron: You have nothing to fear! I have already crushed Optimus Prime with my bare hands!
During Prime's Foe-Tossing Charge, Blitzwing desperately, trying to get out of the way, and just barely suceeding. Especially funny if you look at Prime's Dashboard instead of Blitzwing and realize that as Blitzwing was dodging, Prime was swerving in order to catch him, before giving up and righting himself to charge at the rest of the Decepticons. That's right. Blitzwing only dodged that bullet because Prime couldn't be bothered. Adds an extra helping of humor to what is already an awesome moment.
No the funniest part of that whole sequence was when it started, Prime comes barreling around the corner, Thrust turns around and we see the look of horror on his face, reflected in Prime's grill as he realizes Optimus Prime is here and he's going to run him over.
"Me Grimlock no bozo! Me king!"
And the Dinobots Dynamic Entry into Hot Rod and Kup's trial and flattening the "Bailiff Alien" in the process.
Slag: (to the bailiff, as he's still being squashed) Excuse me!
A Junkion kisses Grimlock.
Grimlock: Me Grimlock no kisser! Me king!
After Grimlock and the Dinobots curbstomp the Sharkticons, we have this.
Quintesson: Sharkticons, execute them!
(The Sharkticons hesitatingly go into robot modes)
Grimlock: (Stomps and shakes the whole room and points at the Quintesson) Me Grimlock say execute them.
(The Sharkticons look at each other for a moment before grinning attacking the Quintesson)
"Me Grimlock kick butt!" (Literally kicks Unicron's butt, then nearly gets crushed) "Me Grimlock need new strategy!"
The entire scene where the Junkions are introduced. It helps that Dare to be Stupid plays during this scene.
After surviving an assault from the Decepticons, Ultra Magnus asks Perceptor if there's anywhere close where they can repair their damaged vessel. Perceptor launches into a ridiculously unnecessary spiel, only to catch Ultra Magnus staring at the ceiling looking completely bored. Even Springer gives him a look that practically shouts "get to the point, man..."
Starscream shooting his own foot to escape Autobot City's transformation. It falls under Amusing Injuries since, in the scale of Transformer injuries, a foot shot is basically nothing.
As the Dinobots fight the Constructicons, Devastator slams Snarl in the back, causing his eyes to bug out and gain pupils for a brief moment.