@Wonder
Oh, I didn't see your edits to your post.
Diamond is hard, but very brittle. If it was hit hard enough, it would shatter.
You see, there's a difference between hardness and toughness.
Diamonds are very hard, but they can't give to any stress, or else they break.
Steel would be considered tough because of it's ability to constantly take punishment and only slightly warp and bend before breaking.
I'll have your list soon.
There has been research into Nano-technology to add both properties to a single material. That's probably what John's armor is made out of, considering that it never shatters (It's made of a Titanium alloy).
You could use Nano-engineered Titanium, or use Carbides.
Another thing to look at would be some kind of Steel-Carbide or Titanium-Carbide.
Titanium-Carbide is meant to not only be strong, but can also resist large amounts of heat (5,000 F).
Titanium-Carbide:
http://en.wikipedia.org/wiki/Titanium_carbideI would also look into Osmium. Osmium is the densest metal known to man. It's a member of the Platinum family and is incredibly hard. It's actually harder than diamond.
That being said, it's still brittle. It can still be shattered if it's exposed to enough shock (blunt/concussive force).
If you go into Osmium, I would recommend an Osmium Alloy, or Nano-engineered Osmium.
Osmium:
http://en.wikipedia.org/wiki/OsmiumThere's also Graphene.
Graphene is a new Nano-material that is as hard as diamond, yet as flexible as paper.
Nothing says that you can't have Graphene armor...
Graphene:
http://en.wikipedia.org/wiki/GrapheneI would recommend looking up more on Graphene. It's basically a miracle material.
The only catch is it's thermal and electrical conductivity.