Drookian Fen Guard
"Up with halberd out with sword, On we'll go for by the lord, Fiach MacHugh has given the word, Follow me up to Carlow"
- – Follow Me Up to Carlow, traditional Irish folk song
"Scotland is not a real country; you are an Englishman with a dress."
- – Soldier, Team Fortress 2
Winners of the coveted Imperial Guard Silliest Name contest for 400 years straight.
The Drookian Fenguard hail from the planet Drook VI. It's pretty much SCOTLAND IN SPESS -- more specifically, the Anglo-Scottish Border, whose men, like the Drookians, were known as reivers and moss-troopers, were natural light cavalry, and feuded a LOT, to the point where the Bishop of Glasgow pronounced a magnificent four-page curse upon them. (The Finreht Highlanders are another candidate for a "Scottish" regiment). It is a Feral World of impenetrable mist, bogs and fens, and as such it doesn't support a big population. The locals largely scrape by via raiding other clans. However, living on such a world makes them natural experts for scouting, guerilla warfare and sabotage.
The Drookians are big on CLAN HONOR and all that jazz; as such regiments raised from the planet, about once a generation, all consist of members of a single clan. They are not big fans of outsiders telling them what (not) to do, not unlike the Catachans. Unlike the Catachans however, the Commissars assigned to the regiments manage to motivate the troops by telling them that the enemy has wronged fellow clan members or insulted their ancestors' honor (which may or may not be true), which gets them to haul ass fast so they can kick the enemy's ass.
The Drookian Fenguard regiments of the Imperial Guard are predominantly light infantry, although there are a number of light cavalry squadrons present amongst them, known for their scouting and infiltration abilities (not to mention their higher-than-average desertion rate). They're often deployed to worlds with harsh environments or noxious warzones (probably to counter their higher than normal desertion rates, so much for clan honor), where their natural abilities and skills can best be put to use. The most violent and skilled soldiers within a Drookian regiment are hand-selected to be used for scouting, guerrilla warfare, infiltration and sabotage. They tend to avoid any markings other than their regiment number, and don't tend to wear any uniform other than the tartan design of their particular clan.
Victoria Lamb's Highland Moss Guard seem to have been made specifically to represent Drookian Fenguard-style regiments, right down to the kilts. Yes, KILTS! (Dead link too.)