If you haven't seen Reconstruction yet, be warned that there will be spoilers in this entry.
What is it that's so great about this particular season of a very comedic and ridiculous take on the Halo universe? Well, let's start with the premise of Red vs. Blue. We have two teams of ridiculously inept soldiers who are "at war" with each other for what they believe is the fate of the universe. Being the ineffective soldiers that they are, their battles usually end in whacky hijinks and the exchange of insults, and they very much keep those personalities in Season 6. A brief summary of the characters and their personalities:
Sarge - Gruff and regimented leader of the Red Team, older, comes up with convoluted plans and ridiculous tactics. His hate for the Blues is only surmounted by his hatred of Grif.
Grif - Lazy comic relief who is smarter than he looks, just unmotivated. Has a sort of love/hate relationship with Simmons.
Simmons - The nerd of the Red Team, enjoys math, sucks up to Sarge every chance he gets.
Lopez - The Red team's robot who can only speak (poorly translated) Spanish. Deadpan snarker.
Donut - (absent from Reconstruction) Guy who wears pink armor and is rather effeminate.
Church - Self-appointed leader of the Blue Team
Tucker - Lazy member of Blue Team who only thinks about picking up chicks.
Caboose - The token cool dude of Blue Team. Probably the most popular character on the show for his ridiculous lines.
Tex - A special ops soldier and Church's ex-girlfriend. The only soldier who can actually do something.
Now, mix these characters with Agent Washington, a completely serious special ops soldier (like Tex) with no tolerance for humor. Surprisingly, this works extremely well (considering the number of ways they could have screwed this relationship up). Together, they are all trying to find a new threat known as the Meta who is killing off Freelancer agents (like Tex and Wash) to obtain their armor abilities and AI, which help them in battle.
Then there is the overarching banter between the Director of Project Freelancer and the Oversight Sub-Committee Chairman. These conversations open every episode in the form of audio letter and alternate between the two, and they illustrate one of the most awesome passive-agressive power struggles I've ever witnessed in any series (and they are never on screen throughout the entire season!). While brief at the beginning of each episode, the subject of the dialogue, while at first seems unrelated, is actually intertwined with the entire motivation of the events of the season.
And if that didn't seem to make things come full circle, the big reveal in the season further seals the deal. When I watch this one moment when Washington fully reveals why the Reds and the Blues were stuck in the middle of a boxed-in canyon in the middle of nowhere, why these Freelancer AI have plagued them and caused all their problems from the get go, and why he needs to put a stop to what Project Freelancer has done and bring them to justice, I am stunned. I always watch the scene and marvel at how perfectly everything is drawn together. I get the same goosebumps during each subsequent viewing of that scene that I got the first time I watched it. The reveal is always fresh; it always keeps me on the edge of my seat; it never gets stale, and that is why I consider this the crowning moment of the entire Red vs. Blue series.
And I can't think of any other series that does that to me.