The best possible items for each vocation that are dropped by both bosses of Newhaven - Muglex Clan Chief and The Corruptor are:
Knight: Soldier Helmet, Brass Armor, Brass Legs, Longsword and Steel Shield.
Paladin: Ranger's Cloak, Ranger's Legs and Refined Bow
Monk: Harmony Amulet, Simple Jo Staff
Sorcerer: Mage Hat, Magician's Robe, Wand of Vortex and Spellbook
Druid: Mage Hat, Magician's Robe, Snakebit Rod and Spellbook
Monk doesn't have a set dropped by the bosses, but can also use the same Soldier Helmet + Brass Set which are dropped for Knights, since it has no vocation. Mages can also use it if they want to.
The items are separated between two bosses:

Knights: Brass Legs and Steel Shield
Monk: Harmony Amulet
Paladin: Refined Bow and Ranger Legs
Sorcerer/Druid: Mage Hat and Spellbook

Knights: Brass Armor, Longsword and Soldier Helmet
Monks: Harmony Amulet and Simple Jo Staff
Paladins: Ranger's Cloak and Refined Bow
Druids: Snakebite Rod and Magician's Robe
Sorcerers: Wand of Vórtex and Magician's Robe
All items are vocation based and are dropped the first time you get the most experience out of the bosses depending on your vocation, it's guaranteed. Then it become rare/very rare drops. They are a good source of gold while staying on Newhaven, each piece of equipment/item is worth 150 gold, so if you plan to stay there until level 20 doing all bestiaries, it's a good source of money for low levels.