Taken from today's weekly update. We've already known about the Halo 1 PC flair, but the rest of these are news to me:
 

 
From TOP to BOTTOM:
 

• The Septagon – This option returns for anyone who links their LIVE account to their Bungie.net account.
• The DMR – A pro weapon for Pro members. Get Bungie Pro to bump up your File Share, render videos, and get this emblem. Active subscriptions bought in Halo 3 or Halo 3: ODST carry over to Halo: Reach, of course.
• Marathon – Play the full version of Marathon: Durandal on Xbox LIVE Arcade to enable the Pfhor Terminal emblem.
• Halo 1 – Enter your Halo 1 PC/Mac product key to enable this emblem. Each key can only be used once, so you’d better stop reading this and grab that key before your brother does. Since we have no way to validate who has played the Xbox version, this emblem is reserved for that dedicated community of computer gamers, with over 50k unique users still active each month, 7 years after release. Thanks for sticking with us. It’s been quite a ride!
• Halo 2 – Automatically available if you played Halo 2 for Xbox on your LIVE account before its tearful retirement. If it’s not active for you, no amount of wheedling will change that, sorry.
• Halo 3 – Take a guess… On the plus side, there’s plenty of time to head to your local purveyor of fine, shrink-wrapped games to snag a copy if you’re the one person who actually reads the news on our site and hasn’t played this game.
• Halo 3: ODST – Ditto.
• Assault Rifle – This fine armament goes to anyone who played the Halo: Reach beta a few months ago.
• Spartan Helmet – CLASSIFIED
• HALO – Like Blamite out of a Needler, these faceplate options can supercombine. Unlock the emblems for Halo 1, Halo 2, and Halo 3 to get this special emblem.
• The Star – Who knows? We haven’t come up with a use for this yet. Maybe we will in the future.

I'd probably use the star because it looks like a dragon ball.

Definitely representing my favorite of the series which is Halo 2.

" Definitely representing my favorite of the series which is Halo 2. "

Oooo, the Marathon one.  It's like a reward for enduring the slight motion sickness that game used to cause before patch.

Halo 2 represent!

The Halo PC one looks a bit poor but at least I get the full Halo emblem, I might use that or the assault rifle. 
 
Maybe the spartan helmet  is for finish the game on legendary or get all armor pieces in the armory which would take a long time.

If I  had Halo PC, id use the "Halo" one.

I'll probably stick with the Halo: CE one, but I might use the "Halo" one too.

The Assault Rifle or ODST for me.... probably the Assault Rifle.

The Marathon one looks the best, followed by the DRM.

I hope I can get the Spartan helmet or the star, if not I think the ODST one is my favourite of the ones I can get.

" Definitely representing my favorite of the series which is Halo 2. "

Has anyone actually played Marathon: Durandul? Just wondering if it's any good.

Those are even less significant than I thought they'd be.

Can't wait to slap that big 2 next to my GT.

Most likely gonna use the Marathon one, if only because its an actual symbol and not a word or gun.

Halo 1 all the way.

" Definitely representing my favorite of the series which is Halo 2. "

Halo 3 all the way! finished the fucking fight!

No! halo! you don't need 10 billion customizables like COD!!

Definitely going for the Halo (PC) one. Simple, effective, stylish. Plus, I only have the Halo 3 one and in comparison just not as cool.

" Taken from today's weekly update. We've already known about the Halo 1 PC flair, but the rest of these are news to me:
 

   

It ain't a flair if it ain't named Ric Wooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo!!!
 
I saw a bloodied and beaten Ric Flair manage to make Master Chief submit to the Figure 4-Leg Lock in a grueling hour long 5-Star classic for the NWA title in the Omni Coliseum. I love me some Halo but for Master Chief to be the man he's got to beat the man. Now how would you ladies like to take a ride on Space Mountain? Woooooooooooooooooooooooooooooooooo!!!

I thought it was going to be an emblem on the armour or something. I don't mind this but was expecting something more.. 
 
Not that it matters, as long as the game's fun.