Southern Trolls:
Smaller, cheaper, weaker but faster and more numerous than regular trolls. They use a custom Troll model made by Dindi, inspired by the trolls of older editions.

Armoured Ice Trolls:
Exactly what it sounds like. Icetrolls with more armour and melee defense.

Cavern Trolls:
A variant of the usual River Troll. They are from the murky deeps of underground lakes, fighting with the monsters of the deep for survival.

Chaos Stone Trolls:
Stone Trolls changed by Chaos or normal Trolls warped into something similar to a regular Stone Troll? Only the Chaos Gods know. These Trolls barely know pain and rely on their hardened skin in melee, however their morale is easily shaken once someone managed to really hurt them.

Forest Trolls:
These Trolls live in forest areas, devouring animals and humans that carelessly wander into their territory alike. They excel at smashing infantry units. However, everything bigger than infantry can become rather problematic. While their skin has taken on a coloration that helps to naturally carmouflage them in forests, the concept of an ambush or sneaking is difficult to understand for their limited minds. However, they are difficult to detect from afar as long as they stay in forested areas. Up close, noise and smell give them away easily.

Bile Trolls:
Descendants of a troll horde which defeated and devoured the army of a Nurgle champion, these trolls are outcasts. They are tormented by many plagues which are barely held at bay by their natural regenerative abilities and neither friend nor foe wants to be anywhere near them. They are slow (for trolls), poisonous, resilient to physical damage, have a huge healthpool and an aura that weakens all the units around them (including allies). They are a bit lower in number compared to other troll units and their version of regeneration replenishes hitpoints slower. Being damn hard to kill (as long as you keep them away from elite-antilarge and/or fire/magic damage) they excel at holding down enemy units while your army is busy elsewhere - or to quickly rout the more cowardly parts of the enemy army.

Snow Trolls:
From the highest peaks of the mountains, eternally covered in snow come the Snow Trolls. A rarer breed of troll, covered in shaggy fur and being bigger than most other troll kinds only few of them leave their high mountain homes to join Throgg. They have a tiny unit size, are anti-large, relatively fast on their feet and hit like trucks. They are quite fragile for their cost though and not the most effective infantry killer compared to their other brethren.

Lava Trolls:
Inspired by a sentence or two from the Chaos Dwarf supplement, the Lava Trolls hail from the Dark Lands and are in many ways one of if not the most unusual Troll species. Having adapted to the heat of their homeland, they resist fire but have lost their regenerative abilities. Still, they radiate so much heat that nearby enemies are receiving damage by their mere presence.

Sea Trolls:
Another unit only briefly ever mentioned in a sentence (and i ignore most of the part about their looks), these trolls hail from the deep sea and are usually only rarely encountered on land. They are famous for ripping a verminlord apart, so they are a strong anti-large aquatic unit. You only get them from ports as you have to lure them from the murky depths of their ocean home.

Giant Troll:
A single entity monster using giant animations, so you are basically getting a faster, more expensive giant with regeneration. Not a ton to say here really, if you know giants and trolls then you pretty much know what this unit is going to be like.

The Bloody Avalanche:
RoR version of Armoured Ice Trolls with better stats, terror and berserk. Very scary once they are in melee, but be wary of amourpiercing anti-large or amourpiercing projectiles. Or fire.

Shipwreckers:
Cavern Trolls dwelling near the harbor of Marienburg. They prey on trading vessels and wear the remains of the destroyed ships on their body. They have better stats, cause terror, and are armourpiercing anti-large monsters with a talent to smash gates.

Throgg's Company:
Norscan Trolls that have been under Throgg's influence for a long time already. With the power of the Wintertooth Crown and his natural talent at commanding Trolls, Throgg managed to teach them to follow four different specific orders relatively reliably - however, only one per battle. More would be too challenging for their Troll intellect and lead to confusion.

Night Trolls:
Coming from the pages of the Citadel Journal, Night Trolls are a rare variation of Stone Trolls said to be found around the Chaos Wastes. They are of darker coloration than Stone Trolls and are known for making noises that sound a lot like mocking laughter when killing their enemies. Their model is based on Urgat's proppa Stone Troll model.

Warped Ones:
Maybe an escaped experiment of Clan Moulder or maybe a freakish mutation under the influence of Chaos, these Stone Trolls have mutated to have a protective layer of Warpstone skin, making them resistant to all damage until the protective layer is broken. They also have contaminating attacks.

Troll Lord
The Troll King can't be everywhere, so he has to appoint someone in his absence. Why not appoint a Troll? They are neither natural leaders nor anywhere near smart, but Throgg can take control of them and lead his armies by proxy. Better than relying on those puny civilized humans, right? Or at least better than no leader at all. Since the strongest and biggest Trolls at least tend to know how to throw a decent punch, they can be useful in battle if nothing else.

Chief Ugma
Chief Ugma is the intelligent leader of a small river troll tribe in Karak Azgal (aka Dragon Crag). His intelligence is probably a byproduct of prolonged exposure to warpstone. He has now been discovered by Throgg and recruited as 2nd in command. In battle he is a slower and more defensive combatant than Throgg or the Troll Lord, but he can still grind down very strong opponents. He also is a minor character from the Warhammer rpg adventure Dragon Crag. Wouldn't go so far to call him canon, but he is no pure fan fiction either.

Chaos Troll Champion
Chaos Troll Champions are melee heroes. Armoured, tough and regenerating they bring their raw might to the table, able to straight forwardly beat down their targets. The vicious brutality can scare other trolls into submission and keep them in line in tight situations.

Sea Troll Hag
A Troll Hag caster wielding a modified version of the Lore of the Deep, allowing her to summon Sea Trolls to the battlefield.

River Trolls
River Troll RoR
Stone Trolls
Armoured Chaos Trolls
Giant River Troll Hag