In Wrath of the Lich King it is item level 200 and requires level 80. In MoP Classic it is item level 200, requires level 80 and sells to vendors for 1c.
In the Appearances collection, Hateful Gladiator's Leather Helm is listed as Vendor. Appearance ID: 10731. No other item uses this appearance, so it is unique to Hateful Gladiator's Leather Helm.
Read from the World of Warcraft client build files.
How Hateful Gladiator's Leather Helm Compares
Who It Suits
Leather is the armor type Demon Hunter, Druid, Monk and Rogue wear. With Agility or Intellect, Hateful Gladiator's Leather Helm suits Assassination, Outlaw and Subtlety Rogue; Brewmaster, Mistweaver and Windwalker Monk; Balance, Feral, Guardian and Restoration Druid; Havoc, Vengeance and Devourer Demon Hunter.
Similar Items
The 10 items nearest to Hateful Gladiator's Leather Helm (item level 35) in item level among Armor > Leather, Head slot, from item level 32 to 37.
Items Numbered Next to Hateful Gladiator's Leather Helm
Blizzard numbers items as they are created, so the named items next to ID 41670 (41664 to 41676) were usually added in the same batch as Hateful Gladiator's Leather Helm: the same quest line, zone, vendor or reward set.