The fight against the Nightmare-controlled Ursa Major is an excellent action scene. The bit with Celestia ‹bercharging Firewall (Kritzkrieg-style, if you must know) so he could send humongous fire blasts at the big baleful bear was particularly intense.
The race between Rainbow Dash and Storm Wing. Now watched by everypony on "TV", with Pinkie Pie as announcer! Rainbow Dash wins.
Storm Wing revealed that he threw the race on purpose, so that he had an excuse to consider her for the Sky Archons.
Fire pulling off a successful and proper 'SHORYUKEN!' against Shadow Shot. This pony knows how to fight!
When Firewall gets Burning with Anger, it's actually rather awesome. Especially when he turns it into a power.
The fact that Firewall, despite being a human-turned-pony in the middle of a war against an all-powerful shadow spirit, with new reveals being made every damn five seconds, manages to keep his cool withfewexceptions, speaks wonders about his restraining ability.
And of course nobody notices how cool it is that Firewall, originally just a simple brony, managed to get Princess Luna, one of the two gods of Equestria, to actually fall in love with him.
Chapter 14 has two counts, one is the powerhouse battle between David and Stephen.
Firewall/Stephen & David's debate on the integrity of ponies. Also doubles as Hartwarming, showing just how much faith Firewall has in ponykind.