Beast Machines/Awesome

The exchange of Hannibal Lectures between Optimus and Megatron when they meet each other again for the first time in the show is simply awesome as they both get under each other's skin.

Optimus: "You're still ruled by emotions. That's not very technologically "pure", is it? You can feel the anger RISING inside you! You're just about ready to explode! {This gets Megatron to go into Beast Mode} Look at yourself, Megatron! See that thing that you despise the most! Cybertron will never be pure as long as the beast exists within you! You failed."
Megatron: "No, Primal, you have failed. You're still too late to save your people. Billions of Transformers, their extinguished sparks are on your hands! Perhaps if you had won the Beast Wars, things would be different. Who's to say? {This makes Optimus angry and revert to Beast Mode} Who's the beast now, Primal?"

In the second to last episode where Cheetor is the ONLY Maximal left functioning and is exhausted, weakened and beaten to crap...and then takes out Thrust, Obsidian AND Strika by himself. First by sending Obsidian and Strika into space and then going one on one with Thrust. During a final struggle he grabs one of the spark extractors and then rips out Thrust's.
Megatron's actions in "The Weak Component" have always seemed his highlight as a character. Crippled and isolated, his army disabled, Megatron is on the verge of defeat by the Maximals...but he uses their divisions against them, to recruit Rattrap for one night and to buy time to regain his strength. And in the end, once he COULD destroy the Maximals, he doesn't... not so much for honor as because he made a bet, he lost, and he always did enjoy gambling. It really highlights BW Megatron at his charismatic, plotting, gambling, megalomaniac best.
The final episode is just one big Awesome Moment with the Optimus Primal vs Optimal Optimus body Megatron fight culminating in Optimus sacrificing himself to destroy Megatron (Megatron's giant facial expressions of fear are incredible!) and to reformat Cybertron.
- Don't forget the epic aerial battle over and under the city leading up to that...
Everything Optimus does in "Fallout." After pulling a massive What the Hell, Hero? and unleashing the Plasma Energy against the Key to Vector Sigma, the clash of energies destroys his physical form, with Cybertron about to follow. The Allspark itself calls him out on it, and Optimus realizes what his actions will lead to. After a little help from the Allspark and Rhinox (and presumably a massive amount of sheer willpower,) his body regenerates. He proceeds to use himself power conduit, channeling the energies through himself and back into their respective sources before being blasted into atoms. The Allspark itself is impressed, and offers to let him join the Matrix, but Optimus opts to finish his mission, upon which The Oracle recreates his body. Like a boss, Monkey.
Noble's last stand, which sees him singlehandedly ruining a large degree of Megatron's plan, while also smacking Obsidian and Strika around.