Combat Servitors are Servitors that do battle on the behest of the Adeptus Mechanicus. Most Combat Servitors specializes in close quarters combat and are thus, often equipped with some form of Power Fist or Power Sword although they can be armed with Heavy Bolters and the like. They usually act as the Mechanicum's equivalent of cannon fodder, although unlike other races cannon fodder, Combat Servitors can break your back and fuck up your Power Armor if you're not careful. These guys are cheap, common, and easily mass-produced.
Types of Combat Servitors
There are several flavors of Combat Servitors, each deadly in their own right.
The Praetorians are the Big Cheese of the Servitor family. Praetorians are a class of heavily armed and armored Servitor that are created by the Adeptus Mechanicus to guard the shrines and temples dedicated to the Machine God from direct attack. They are commonly built with tracks or jointed mechanical legs to allow for easier mobility and to support their immense weight. The reason why they sound huge and menacing? Because these Servitors are made up of former Orgyns, you know those 3 meter tall, dumber than an Ork, bone crushing and ceramite cracking dudes. While their fearsome presence alone is enough to generally discourage attack, they also have the power and weaponry to back up their threatening appearance. Praetorians tower even over Space Marines in battle. Their duties are not limited to just guarding temples, as they often serve as bodyguards to Techpriests on the battlefield. Although they are Servitors, the Praetorians are held in high esteem by the Skitarii who fight alongside them.
Clipaeus-class Combat Servitor
Clipaeus-class Combat Servitors are a much rarer bunch than their more common brothers. They are typically reserved for Tech Priests who have proven their worth to the Lathes. The Lathes Mechanicum maintains limited reserves of these servitors to assign as protectors/bodyguards to those of those attached to the Imperial Guard who have similarly proven themselves as assets to the efforts of the war effort. Their rarity is due to possessing a rare and expensive protective field generator that allows it to shrug off deadly blows again and again over the course of continued service (Like energy shields in other Sci-Fi works). Other than the shielding the Servitor is also armed with a electro-gladius for close combat. The Tech-Priests granted the protection of a Clipaeus-class servitor find no better guardian for their work on the battlefield, as the whole of the pattern's advanced construction is geared towards delivering lethal retribution upon would-be assailants.
Lathe Pattern Breacher Servitor
These Servitors were originally deployed to mining colonies and are thus fitted with mining equipment such as the adamantium-tipped drills that replaces both hands (What, you thought Adamantium was rare? Naaah, we just tell the Guard that so they'll die more because it's funny.). Apparently, their mining efficiency is so good that the Mechanicus saw some potential in deploying them in the battle. Thus the Lathe-pattern Breacher Servitor sees considerable combat use among sappers and siege regiments. Its drills allows the Servitor to break into enemy strongholds as easy as it were unearthing ore deposits far from the front lines. Tech Priests well-versed in the rites of servitor cogitation mechanisms sometimes find it appropriate to develop protocols for applying the drills to smaller-scale clashes as well, allowing them to direct the piercing bite of the drills at heavily armoured enemies. By this means, a Breacher Servitor can be the bane of not only a fortress wall, but the elite troops guarding it.
Pugnis-class Combat Servitor
Pugnis-class Combat Servitors are commonly used as a combination bodyguard and shock troop by the soldiers and auxiliaries of the Adeptus Mechanicus. It has a relatively robust frame that is equipped with two massive servo-fists that can assume the correct body positioning to perform a horrifying and painful act of fisting, ensuring the enemy may never shit properly again. Many Tech Priests placed on the front lines of battle owe their lives to the impressive strength these Servitors wield in their defence. The most martially inclined among the Red Priesthood sometimes gather groups of these servitors together for assaults on enemy positions.
Spatha Pattern Combat Servitor
Like the Lathe Pattern Breacher Servitors, these were originally a heavy-duty utility Servitor that could operate in hazardous conditions without the worry of corrosion in its metallic joints or malfunctioning of the wires. Apparently these Servitors reached notoriety during the ill-fated Siege of Cyclopea. Home to a host of Imperial research stations manned only with Servitors, three raider vessels entered the star system in the hopes of boarding and pillaging whatever they could before Imperial forces could respond. The Fabricator that controlled the network of Cyclopean stations had no choice but to do the unthinkable, and modify the Spatha engram patterns so that he could repel the invaders. For some reason left unexplained, these Servitors seem to perform much better in combat than in their civilian duties. Which raise questions on what type of shit the Mechanicus has accidentally programmed in your Servitor Butler and whether or not all civilian Servitors are super combat ninjas in secret. This potential tech-heresy took a further 50 standard years for the leaders of the Lathe Worlds to sanction the Fabricator's variant design, a relatively short approval period by Mechanicus standards seeing as how the Tech Priests like to spend 90% of the time jamming their robotic cocks in their toasters. In more recent years, Spatha Pattern Servitors have been pressed into service as bodyguards in some of the more remote areas of the Lathe Worlds. They are equipped with heavy armor and mechanical attachments of varying degree. Part of the reason for their combat effectiveness might be due to the fact they are based on human brains...and humans are vicious, violent, and savagely brutal combatants. Unleash that in tight confines with tools meant for breaching and breaking things far stronger than normal armors and, well, yeeeeahhh.
Velox Pattern Security Servitor
Essentially roided-up Servitors on cocaine. These Servitors are found mostly on research stations across the Lathe Worlds, as well as Explorator vessels leaving the Calixis Sector for regions unknown. The Velox Servitors are some jacked up motherfuckers. They are exceptionally fast and overly-aggressive; programmed to track down and eliminate would-be intruders. Tightly bundled coils of vat-grown muscle give the Servitor its incredible speed and dexterity, and its arms each mount an integrated coil-whip, which the Velox tends to use in a frenzied spinning motion, pulverizing whatever happens to be in its way. Kept dormant when not in use, they are rightly feared by friend and foe alike. No they should not be confused with the Arco-flagellants.