There's two that dominate that area.
Ravenstern Rangers (And to a lesser extent, mounted rangers) are the elite "Archer" unit (Not counting special units, such as the Noldor, or Silvermist Rangers). They fire quick and deadly, but they also run out of ammo fast. They usually spawn with two handed swords, so they also make surprisingly good anti-cavalty or siege units.
The Empire Armoured Crossbowmen are the crossbow varient. They fire slower, but hit hard, and their ammo lasts longer. They're a bit more beefy than the Rangers. A much more well-rounded unit in my opinion, while the Ravenstern Ranger is more specialized.
Pick your flavor.