Thunderwolf Cavalry

You may joke how he is 'riding his mount' but this is one wolf you don't want to fuck with.

The Thunderwolf Cavalry (AKA The Alpha Furries) are a small elite unit of the Space Wolves who ride massive Fenrisian Thunderwolves into battle. These warriors do not appear in any official Imperial records, and are seen so rarely in combat as to be considered almost mythical. The Space Wolves continue to officially deny the existence of these cavalry.

Thunderwolves are truly monstrous animals: they can grow as high as eight feet at the shoulder, their thick fur is as dense as steel wire, and their jaws, filled with enormous and rapidly replaceable teeth, can chew through steel. They are solitary by nature, attacking each other on sight, as if each one is seeking dominance over all other wolves on the planet. They are the apex predator on Fenris with no exception.

According to rumour, capturing and "breaking in" a Thunderwolf is an initiation rite among the upper ranks of the Wolf Guard, and some of these warriors have demonstrated enough control over their wolves to tame them as war mounts, which are often augmented with adamantium jaws, hydraulic strength enhancements, and razor-sharp metal claws.

At least one high-quality vid-steal exists of Thunderwolf Cavalry riding in battle against a mob of heavily-armoured Ork Nobz.

In 954.M41, Logan Grimnar deployed his elite Thunderwolf riders to hunt down the enormous and terrible Abomination of Cyriax, terrorizing Hive Necros. Though only glimpsed, the legend of giant warriors riding metal-skinned wolf-daemons spread across the entire planet. Why it is so damned hard for the Imperium to get proper record or evidence for giant, 8-foot tall, hulking wolves the size of rhinos being ridden by an equally large Space Marine, and why the Space Wolves would care that the Imperium knows that they have found yet another way to take a dump on the codex, is a source of mystery. Maybe Creed was involved somehow? Knowing the Space Wolves, they do it for sheer amusement.