Tier 9

The tier 9 is armour sets are faction specific,so the Horde and Alliance look different from eachother, however the armour types are a little similar as you will see.
Tier 9 is found inside the Trial of the Champions raid instance in Icecrown, a raid instance with no trash so a nice quick run with a good group.
Lets start with the Death Knight sets.

Death Knight

Thassarian's Plate -  Alliance

Trueheart Girdle
Sabatons of the Lingering Vortex

Koltira's Battlegear - Horde

Girdle of Arrogant Downfall

Dawnbreakers Sabatons

Level 70 Brutal Gladiator's Gear - Death Knight

Back in The Burning Crusade, arena was first released, which added another way to PVP, and if I remember correctly, all the arena gear required an arena rating, so I think it was quite rare to see a character with full Brutal Gladiator gear, although now, it is sold by the Legacy Armour Quartermasters in Orgrimmar and Stormwind

Both Alliance and Horde got the same models, but the armour types for each class (mail for Shamans and Hunters for example) stayed the same, just recoloured.

Back in Wrath, Blizzard were kind enough to add a level 70 PVP set for Death Knights!

Brutal Gladiator's Dreadplate
Guardian's Plate Greaves

Plate Look-a-likes

Mentioned in a previous post, The Burning Crusade instances dropped items that are recoloured tier 2 raid sets. These sets have no class requirements so Death Knights rejoice (you can run around looking like a Paladin or even a Warrior, and Warriors can look like Paladins, and Paladins can look like Warriors, ohhhh think of the confusion and the laughs it willl cause!)

So to start this little 'Look-a-like' section of posts here are the tier 2 raid plate look-a-likes!

Greathelm of the Unbreakable
Fanblade Pauldrons
Jade-Skull Breastplate
Thatia's Self-Correcting Gauntlets
Greaves of the Shatterer
Boots of the Colossus
Girdle of the Immovable
Deathblow

Mask of Penance
Justice Bearer's Pauldrons
Breastplate of Many Graces
Life Bearer's Gauntlets
Cassock of the Loyal
Boots of the Watchful Heart
Girdle of Many Blessings
Aldori Legacy Defender
Continuum Blade

Endbringer!

So, I was listening to this Dethroned - X Ray Dog and all that was swirling around in my head was a kickass looking warrior Bladestorming in a battleground, and this set is how I saw him. So you could say this was a vision from my mind. In truth, I thought this was cool and had jack to say about it.

Overlord's Chestplate
Saltstone Shoulder Pads
Overlord's Legplates
Deathbone Sabatons
Deathbone Gauntlets
Enchanted Adamantite Belt
Helm of the Thousand Needles
Endbringer
Tabard of the Argent Crusade

Cracking Skulls

Ey mon! Dis troll be crackin' da skulls. You can't own a Troll without transmogging it back to their voodoo glory. If you are unable to get the recent gear in Zul'Aman, it is possible to obtain the old Burning Crusade badge gear which have very similar styles.

High Chief's Crown
Pauldrons of Gruesome Fate
Plate of the Shaman King
Bloodthirster Wargreaves
Giant - Sized Gauntlets
Bladed Steelboots
Exalted Girdle
Hate Forged Cleaver

Death Knight

The head on this one is a Holy Pally boss drop, it makes a nice change from the usual skulls and scary stuff that Death Knight armor always consists of. As far as I know you can Trangsmog an item which is the same armor type, but has useless stats on, so as a Death Knight you can use Holy Paladin gear.

Hellfrozen Bonegrinders
The Untamed Blade
Bloodbath Girdle
Brutal Gladiator's Dreadplate Shoulders
Doomplate Chestguard
Doomplate Gauntlets
Doomplate Legguards
Dory's Embrace
Faceguard of the Eyeless

Death Knight Love

As Death Knights started in Wrath they missed out on having the old tier sets to obtain, but that isn't the end of the world. There are many off set pieces and look alikes to keep and old DK happy.

WoWWiki look alike site  will help you find sets that will make your DK look a bit more brighter, with less skulls.

The Worgan DK look in the first picture is made up of the following:
Myrmidon's Treads
Grips of Silent Justice
Leggings of Divine Retribution
Helm of the Illidari Shatterer
Belt of Seething Fury
Chivalric Chest
Frostblight Pauldrons
Shroud of Forgiveness
Slayer of the Lifeless

Scarlet for Plate

The Scarlet Crusade have an item set (Chain of the Scarlet Crusade) that drops in the Scarlet Monastery, however these items are mail and due to the restrictions of transmogrification can not be used by plate wearers.

The Scarlet Tabard is the most important part of this, and can be looted off the Scarlet Trainees which appear after Herod is killed in the Armory, however it has a low drop rate so a little bit of farming may be in order.

Ragesteel Helm
Darksoul Shoulders
Ragesteel Shoulders
Darksoul Breastplate
Khorium Belt
Ragesteel Gloves
Darksoul Leggings
Khorium Boots
Ravager
Aegis of the Scarlet Commander
Ironspine's Fist