EH - Austere Earthsiege Diamond: The 32 stamina on this meta is common to a few other meta gems, but the 2% armor bonus makes it the gem of choice for the EH set.
AV/BV/T/UH - Eternal Earthsiege Diamond: 21 defense rating isn't a whole lot, but if you need a little defense to get you over the cap, or you are already at the EH threshold for the content you're tanking, you can put this gem in your Avoidance helm, your block value helm, or your threat helm for that matter. The set that benefits the most from this meta will be your Anub adds "passive unhittable" set.
EH - Solid Majestic Zircon: For a pure EH set, unless you have a stamina socket bonus you'll want to put this gem in every possible location (don't forget to include one red gem in your EH set for your meta to work).
AV - Enduring Eye of Zul or Regal Dreadstone
T - Guardian's Dreadstone
BV - Sovereign Dreadstone
UH - Thick King's Amber. You'll be using these pretty much exclusively for the Unhittable set, ignore socket bonuses and just stack defense for this set.
EH - Solid Majestic Zircon: again, use this unless there's a stamina socket bonus (in which case you can substitute a gem that matches the socket color and gives you 15 stamina + dodge or defense or whatever)
AV - Subtle Cardinal Ruby, Stalwart Ametrine, or Regal Dreadstone. The parry gems aren't going to get you anywhere.
T - Precise Cardinal Ruby or Accurate Ametrine are both great, also Guardian's Dreadstone or Resolute Ametrine if you are looking to add stamina or defense rating.
BV - Bold Cardinal Ruby: You'll be using your BV set on trash mostly, and you'll probably reach the 177 hit / 22 expertise caps easily, so stacking strength gems is the next best way to increase block value.
UH - Thick King's Amber. It's best to ignore socket bonuses and stack defense gems for your unhittable set.
EH - Solid Majestic Zircon: yet again, use this unless there's a stamina socket bonus (in which case you can substitute a gem that matches the socket color and gives you 15 stamina + dodge or defense or whatever)
AV - Thick King's Amber is the best, followed by Stalwart Ametrine and Enduring Eye of Zul.
T - Accurate Ametrine again, nice threat gem mentioned earlier for either a red or yellow socket.
BV - Anything with strength on it
UH - Thick King's Amber:
I'm indebted to Veneretio for his great post on Warrior 3.0.8 Tanking Enchants. I've applied basically the same enchants he lists to the gear I've placed in the three categories (EH, AV, T). I've expanded on his work a little, but I'm not going to take credit for most of this section (no sense trying to re-invent the wheel anyway).
EH - Arcanum of the Stalwart Protector (Argent Crusade Revered):
AV/UH - Arcanum of the Defender (Keepers of Time Revered): technically more avoidance than the new tanking head enchant--if it's worth it to gain a little avoidance at the expense of 37 stamina, then use this. Unless you're trying to absolutely max out avoidance for some reason (read: unhittable set) it's best to stick with the Argent Crusade head enchant.
T - Arcanum of Torment (Knights of the Ebon Blade Revered):
BV - Presence of Might (Zandalar Tribe Friendly): Yea... kickin it old-school style. If you have one of these sitting around or you want to farm ZG to beat the boredom, you could technically still use one of these on your BV set.
EH - Greater Inscription of the Gladiator (30 stamina, 15 resilience rating):
AV/UH - Greater Inscription of the Pinnacle (20 dodge rating, 15 defense rating):
T - Greater Inscription of the Axe (40 attack power, 15 critical strike rating):
EH - Mighty Armor (225 Armor):
AV/UH - Titanweave (16 defense rating):
T - Major Agility (22 agility)
EH - Super Health (275 health):
AV/UH - Greater Defense (22 defense rating):
T - Powerful Stats (10 to all stats)
EH - Major Stamina (40 stamina):
AV/UH - Major Defense (12 defense rating)
T - Expertise (15 expertise rating):
EH - Heavy Borean Armor Kit (18 stamina) OR Glove Reinforcements (240 Armor):
AV/UH - Major Agility (20 Agility):
T - Armsman (2% threat increase, 10 parry rating):
EH/AV/UH - Frosthide Leg Armor (55 stamina, 22 agility)
T - Icescale Leg Armor (70 attack power, 22 critical strike rating):
BV - Presence of Might (Zandalar Tribe Friendly):
EH - Tuskarr's Vitality (15 stamina & run speed increase) or Greater Fortitude (22 stamina):
AV/UH - Superior Agility (16 agility):
T - Icewalker (12 critical strike rating, 12 hit rating):
EH - Blood Draining
AV/UH - Exceptional Agility (26 agility)
T - Accuracy (25 critical strike rating, 25 hit rating):
EH - Major Stamina (18 stamina) OR Titanium Plating (40 block value):
AV/UH - Defense (20 defense rating):
T - Titanium Shield Spike (45-67 damage on blocked attacks):
BV - Titanium Plating (40 block value):