As of Blood of Gladiators release date:

Heroes

• Kil'zin of the Bloodscalp (SotB)
• Jonas the Red (SotB)
• "Black Ice" Fizzlefreeze (HfI)
• Zaritha (HfI)
• Illidan Stormrage (BT)
• Varanis Bitterstar (PROMO)

Alliance Allies

• "Chipper" Ironbane (TDP)
• Korthas Greybeard (TDP)
• Champion Zosimuus (MotL)
• Antikron the Unyielding (SotB)
• Myriam Starcaller (SotB)
• Rysa the Earthcaller (SotB)
• "Scrapper" Ironbane (HfI)
• Defender Nagalaas (HfI)
• First Responder Avaressa (HfI)
• Instructor Giralo (HfI)
• Talian Bladebender (HfI)
• Weldon Barov (DoW)

Horde Allies

• Hur Shieldsmasher (HoA)
• Nyn'jah (TDP)
• Waz'luk (TDP)
• Bloodsoul (MotL)
• Doshura Risestrider (MotL)
• Sha'kar (SotB)
• Vexmaster Nar'jo (SotB)
• Blood Knight Kyria (HfI)
• Offender Gora (HfI)
• Cromarius Blackfist (DoW)
• Himul Longstrider (DoW)
• Johnny Rotten (DoW)
• Joja'bee (DoW)

Neutral Allies

• Sayge (DMF)
• Marksman Glous (SotB)
• Xanata the Lightsworn (SotB)
• Water Elemental (HfI)

Mage Abilities

• Counterspell (HoA)
• Spellsteal (TDP)
• Fizzle (FoO)
• Nether Fracture (MotL)
• Invisibility (SotB)
• Metalmorph (SotB)
• The More, the Scarier (HfI)
• Conjured Cinnamon Roll (DoW)

Rogue Abilities

• Eviscerate (HoA)
• Purloin (TDP)
• Pick Pocket (FoO)
• Gut Shot (SotB)
• Overkill (HfI)
• Hateful Strike (BT)
• Deathblow (DoW)
• Detect Traps (DoW)
• Surge of Adrenaline (DoW)

Shaman Abilities

• Lightning Bolt (HoA)
• Earth Shock (FoO)
• Fire Elemental Totem (FoO)
• Stoneclaw Totem (MotL)
• Death Shock (SotB)
• Storm Shock (SotB)
• Crackling Purge (HfI)
• Lightning Arc (HfI)
• Grounding Totem (DoW)
• Primal Totem (DoW)

Other Abilities

• Cannibalize (TDP)
• Engulfing Blaze (DoW)
• Spell Suppression (DoW)
• Thud! (DoW)

Equipment

• Perdition's Blade (MC)
• Whispering Blade of Slaying (MotL)
• Retainer's Blade (HfI)
• Black Amnesty (DoW)
• Belt of Blasting (CRAFT)

Quests

• Chasing A-Me 01 (HoA)
• Counterattack! (HoA)
• Kibler's Exotic Pets (HoA)
• The Defias Brotherhood (HoA)
• Finkle Einhorn, At Your Service! (TDP)
• Solanian's Belongings (TDP)
• Corki's Ransom (FoO)
• One Draenei's Junk... (FoO)
• Swift Discipline (FoO)
• Falling to Corruption (MotL)
• Forces of Jaedenar (MoTL)
• Dr. Boom! (SotB)
• Marks of Kil'jaeden (SotB)
• Orders From Lady Vashj (SotB)
• Tabards of the Illidari (HfI)
• The Fel and the Furious (HfI)

Locations

• Towers of Eastern Plaguelands (DoW)

Rares

• Vengeful Gladiator's Vestments
• Felsteel Whisper Knives
• The Darkmoon Faire
• Prince Kael'thas Sunstrider
• Lady Vashj
• Lady Katrana Prestor
• Invocation
• Slow
• Mystic Denial
• Blade of Wizardry
• Seer's Signet
• Earth Elemental Totem
• Mana Tide Totem
• Totemic Recovery
• Rescue the Survivors!
• Aegis of the Vindicator
• Owned!