Riding into battle on the best steeds Rohan can offer, the Royal Guardsmen can go toe to toe with any cavalry in the game and win. A specialized formation also lets them disrupt foot troops effectively. They are expensive however, and limited to two units on the field at once. Royal Guardsmen also have the Sons of Eorl passive special ability, which grants them +50% to the effectiveness of any Leadership bonus recieved from a Rohan hero. They are purchased at a Rank 3 Stable, and can receive the Banners upgrade - all the others are inherent.
Skilled at defence, a second branch of the King's Royal Guard is dedicated to the defence of Rohan's capital. These warriors are strong, having access to two useful abilities - Defenders of Rohan gives them bonuses when near friendly Farms, and Lock Shields gives them bonuses to their already formidable combat capabilties. They can recieve the Banners upgrade, and are purchased at a Rank 3 Archery Range. Like their mounted cousins, only 2 units can be active at once.
King's Guard of Meduseld
You'll just have to wait and see!
The Scouts of Isengard are tough, fast and nasty. Elite troopers, they can switch between short-ranged but deadly bows and swords and shields. Scouts are important as they are now the only Isengard unit that can get Fire Arrows. They also have a much higher attack rate that the sluggish Crossbowmen, so are better on the move. A Rank 3 Uruk Pit is needed to train Scouts. They can purchase Forged Blades, Fire Arrows and Banners. The lack of Heavy Armor makes them better skirmish troops than frontline ones, though they are intrinsically tough.