Just before The First Battle of Reach, all remaining SPARTAN-IIs were given Mark V MJOLNIR Armor. These suits had shields, no bio foam dispensers, but could support an A.I.
Later in the skirmish on Reach, almost all of last spartans (Kelly, Fred, Isaac, and Vihn) receive a upgrade of their Mark V (for simplicity I'll call it Mark V.I) from Halsey. The Mark V.I armor, was a certain piece of armor that gave them a special benefit (for example: Kelly received an improvement to her neural induction circuits, giving her twitch response time a speed boost).
Hope that answered any questions on the topic.
Edit: To the above post: It hit his thruster pack, which was not protected by his armor's shields. As for Halo Wars, in game, the Spartans had a second heath bar similar to the stamina bar in ODST. However, Ensemble (now Robot) decided to give the stamina's recharge a shield sound to make it more familiar. As you can prove, all it did was confuse people (no offense intended).
~Hunter
[Edited on 06.13.2009 10:12 AM PDT]