i toggled my helmet off in my second Firefight game at Comic Con. Its pretty cool. There's also an assist medal, not shown in the above pic. One in that pic is the super detonation medal (plasma pistol + headshot). Its the orange and green one in the bottom right. You can tell cause in the last pic you posted, he was awarded both the headshot medal and the detonation medal and his secondary is the plasma pistol.
*Update* Just put the ViDoc in the first post, be sure to check it out if you haven't seen it. Cool, you went to Comic Con... so did you prefer anything about ODST to Halo 3?
The Needler medal isn't new in is in halo 3 campaign. On that list, none of those medals are new. Also LightScout225 The orange and green one is in halo 3 campaign.
I was looking around in the source code of the new stats system on bungie, and I found a new medal, at least, I think I did. (I'm not sure about the campaign medals) here it is; I believe it is awarded for an headshot, since it is called headshot.gif If I'm right, using the pistol will earn you alot of medals!
Ill be playing as Romeo and will probaly have the helmet off most of the time just to make him more badass.
YouTube - Halo 3 ODST Firefight on Windward in this video, at EXACTLY 9:24, there is a new medal, dream crusher. it's like Slice N' Dice, or open Season, but with a hammer. there is also a hammer spree medal.