Carabineers (ETW Unit)
They are a highly mobile unit, with enough long-range firepower to hurt many enemies; the pistols used by some cavalrymen are only really suitable for close-in fighting during a melee. Their carbines fire a smaller ball than the muskets of infantrymen, but it is still large enough to maim and kill a target. Having the speed of light cavalry, these men are a useful force for any general: they can be moved quickly to a key part of the line to give fire, and then redeployed with equal speed. They are also remarkably difficult opponents for heavy cavalry; it is hard to come to grips with an enemy who can simply outpace you!
Historically, the carbine was only a smaller calibre version of an infantry musket. The idea to cut down the barrel only emerged when it became clear that reloading a full-length musket on horseback was a horrible job, even if the enemy weren't trying to kill you at the same time. Attaching the carbine to the user by a sling finally made it into a very practical, deadly weapon.
Carabineers are similar to dragoons in that they can act as both a light cavalry unit in a scouting role while also providing fire support. They will not fair well in melee due to low numbers and inferior melee statistics. Carabineers are not as numerous as Dragoons per regiment, but do have slightly superior statistics.