I don't think i can pick one best ep of all, but some of my favourites are: G1 - "Day of the Machines", "Prime Target" (Prime was just really cool in these particular eps for me.) and "The Return of Optimus Prime" (The glorious return of the best Autobot leader of all, Rodimus gets kncocked out by him, all is right again in this fan's world, what more can i say?) BW - "The Agenda" eps are what got me into TFs seriously. They were epic and tied G1 and BW together with the discovery of the Ark. Also, the "Nemesis" finale eps were when things really seemed to get serious and desperate for the Maximals, and Depth Charge's death still resonates with me to this day. BW Neo - Quite a few here: - "Move Out Big Convoy!" (The badass introduction of one of my fave Convoys of all! Right from the 1st ep, Big Convoy is obviously not like other leaders, he hates working with others which was very interesting to me. He even shoots at his own troops!), - "Mirage in the Sand" (Possibly the best animated ep of the series imo.), - "Dinosaur Combiner Magmatron" (Big Convoy's mental transition from his old loner ways into a the role of a teacher was nicely addressed in this ep.) - "The Last Battle" (The final epic battle agaisnt Unicron, and Big Convoy gets a suped up 'Matrix Buster' Canon!). RiD - "Commandos" and "The Volcano", these were my fave Decepticon eps, and Scourge/Black Convoy (my first TF love!) was at his best in these first couple of eps after his introduction. Armada - "Mortal Combat" a good ole' no-holds-barred fight between (a literally darker) Prime and Galvatron. Great fight to watch and beautifully animated. TFA - "Thrill of the Hunt" (Ratchets memories involving Arcee were beautifully touching and tragic) and the seasons 1 & 3 finale eps: "Megatron Rising" and "Endgame" (The most climactic moments of the series and many of the best character moments were done in these finale eps. And who will ever forget the death of Prowl?).