Hard for me to pick one but one is very memorable. Season 3 episode 13 - Deadlock when Bee dies from being shot by Megatron he's then ressurected by the cyber matter. Bee then kills Megatron with Primes star saber. Then Bee tells Megatron as he's dying "You robbed me of my voice, you will never rob anyone of anything ever again". EPIC! Gave me goosebumps.