The Main Force
Formerly listed as Daemon Hunters within the army lists from Games Workshop, the Grey Knights are easily one of the most powerful armies you could field in a game. Not only is the majority of the army made up of Space Marines, but each of these Space Marines could fight on equal footing with the lead units of other armies.
Almost every Space Marine model in the army carries a Nemesis Force Weapon. I believe the most notable exception would be the special character Castellan Crowe. Crowe’s Blade of Antwyr (Crowe’s sword) is treated as a normal close combat weapon. Furthermore, all Grey Knight marines are Psykers as well. While their available psychic powers are limited, and differ per unit, these powers make even a basic troop squad a force to be reckoned with.
Inquisition
If the Space Marines weren’t daunting enough, there is also the Inquisitorial side of the army. The Inquisition contains the Inquisitors and their retinues of of minions. Some of the named Inquisitors can even match the ferocity of the greatest Grey Knights. Inquisitor Valeria wields powerful weaponry collected from the corpses of her enemies. The Dagger of Midnight, her close combat weapon, is the epitome of a “double-edged sword.” If she rolls doubles on her two extra attacks, the attacks hit her instead.
My History with Grey Knights
I’ve never faced Grey Knights in a game, as either their own army or an ally unit of the main force. I however do run a contingency of Grey Knights in my Space Marine Apocalypse army. I field Brother-Captain Stern leading a squad of Terminator Grey Knights. I also recently acquired a Dreadnought with a Nemesis Force Sword close combat weapon, unused as of yet.
The last time I ran my Apocalypse army, I think I only lost one Grey Knight. Even though I deployed them with Deep Strike rule right in front of the enemy army they held until the remainder of my army caught up. One day, I do hope to expand my Grey Knight collection enough to create a separate standard army with them.
It’s rare to see Grey Knights fielded in any capacity, mostly because there were limited options on models until the past few years, but if they are used it will be no easy battle for their opponents.