Giant Rat King

The Cat and the Old Rat, Gustave Dore, 1868

In the Blue Book, most of the humanoids are led by exceptional types (kobold leaders fight as gnolls, goblin leaders fight as hobgoblins, etc). In B2, Gygax extends this conceit to the giant rats who live in association with the kobolds in Cave A of the Caves of Chaos: "but their leader (rat #18) who will be at the back of the pack, a huge fellow (DX 12, AC 5 due to speed and cunning, HD 1-1, hp 4, #AT 2 , D 2-4, i.e., 1-3 + 1) wears a thin silver chain set with 5 small gems" (pg 15). This is a step up from the standard giant rat in terms of hit dice, attacks, damage and speed, and gives us another monster variant to add to the Blue Book Monster List:

Giant Rat King

Move: 180 feet/turn, 90 feet/turn swimming
Hit Dice: 1-1
Armor Class: 5
Treasure Type: Q
Attacks: 2
Damage: 2-4 hit points

For every 15 giant rats encountered, one will be a leader of exceptional size, speed and cunning (typical giant rat dexterity is 8; typical leader dexterity is 12), who commands his minions from safety at the back of the pack. When forced to, these leaders attack twice (bite and claws). They have a fondness for gems and jewelry such as necklaces. They otherwise conform to standard giant rats.

Postscript: While looking for an image to go with this post, I came across this disturbing article about real-life "Rat Kings" (tangled rats).