I concur with TTGL, and here are
some of mine lest I bore you with all of them. This post will be most SPOILERIFIC, so be warned.
1. Episode 25, Death Note. If you've ever watched this series, this picture should jog your memory:
2. One Outs, Episode 11. When he explains Johnson's restrictions and how he really isn't a threat, that is when he turns his team into championship material as they truly believe in him.
3. Say what you will, but the Ulquiorra Fight in Bleach was the pinnacle for both animation and how GAR Ichigo can become Episode 271 I think it was? That defined how much of a true "Shonen Hero" he is. Godmodes can be defining moments, I think.
4. Last Episode, Higurashi No Naku Koro Ni Kai, showing how no matter how hopeless you think your fate is, you can shatter it with the right pieces. 100 years of repeating the same month over and over and dying ad nauseum like a demonic groundhog day, growing tired of losing every time.. to finally shatter fate.
5. Episode 7, Baccano! -"Everything Starts Aboard the Advenna Avis" - explains the much needed back-story to give this the true feel of a deep anime, and succeeds.
I could rattle on and on, but those are just some that stick out at the moment for me. I know if I thought on it, there are tons of better examples then these, but I've been up all night and it's not 8:34 am in the morning. /anime then sleep.