G1 Pre-movie:
Optimus getting blown up and tumbling down the mountain side. Such a scary moment as a kid.
TFTM:
A lot of folks have mentioned the great moments in this film, but I want to say the part that still gets me is at the end when Hotrod evolves into Rodimus Prime, and you r hear Optimus says, "Arise Rodimus Prime". Still gets me every time.
Post TFTM:
So many moments to choose from, but the best has to be the Return of Optimus Prime. Not only do we get the hate plague, but we get Optimus coming back, working with Galvatron, and then even having a ceasefire between the Autobots and Decepticons at the end. It was the last new TF episode I saw as a kid, and to be honest it was a good one to go out on.
G1 Comics:
#5 All are dead. Perfect way to continue the story after the massive success of the four parter mini-series.
G2 Comics:
Making Planetfall without a spaceship is not recommended. Or something like that. It was an epic moment where Megatron, thought dead, comes back to help save the day. G2 was where we started trying to give Megatron some redeeming characteristics. In the G2 comic that hinted that Megatron had changed since the destruction of Unicron, the evil influence upon him and other Decepticons had gone.
Beast Wars:
Dinobot's Death was epic, as was the arrival of Ravage, the reveal of the Ark, and the Cliffhanger of Optimus getting shot in the face. Finish the quote Megatron, "Nor would he yield!". That was a great scene!
RID: Omega Prime was epic!
Armada:
No comments.
Energon:
"Scorponok, Be my shield."
Animated:
Not even going to spoil it. But when you find out why Ratchet is with the Ark, and the Ark gets fully repaired...
Bulkhead being the Space bridge genius.
Bumblebee's basic training episode.
Megatron getting taken out in the first episode, and his eventual return, "Decepticons, Transform and Rise up!" Perfect phrase for the Cons.
Starscream and his personalities.
Prime:
The rock getting killed in the first episode.
The entire ending of season 1. Seriously that Arc made this series so epic. With the fallout from it going into season two with Optimus not remembering anything about the Cybertronian wars.
The Zombie Insecticons, that episode was creepy! Hate thtat Blackout didn't get a chance for revenge.
Starscream's redemption. Honestly, this was probably the best Starscream has ever been in a series. He gets exactly what he wants, rules the Decepticons, loses battle after battle, then is exile, realizes the error of his ways, and legitimately joins Megatron as a loyal Decepticon. Add to this the moment when Megatron saves him, "Don't make me regret which one I chose to save"
Bumblebee speaks. That ending episode was so epic. Megatron has killed Bee, and he drops into the stuff below him, regenerates, and saves Optimus by killing Megatron while saying his first line of dialog in the series. EPIC MOMENT!