The Outcasts dance around the jaws of death...Space Marines
Rangers are useful all the way through the game and are the main factor contributing to the ridiculousness of this matchup. Space Marines lack effective detection in the early tiers, the fragile Skull Probes being their only option. Rangers begin the game killing Scouts and remain a thorn in the side of the morale-vulnerable Tactical Marines and Terminators all the way throughout the game. Should the Space Marine player opt for Scout Snipers, Rangers should be used to deal damage to the Scouts in short bursts while a Farseer causes them to waste their valuable shots.Chaos Space Marines
Rangers are, once again, very effective in this matchup during the early stages of the game. Their ability to deal a large amount of damage in a single volley can be used to do horrific damage to unreinforced Cultist squads. If the enemy purchases detection for said Cultists, Rangers can be used to dance around LP2s while the Cultists are ripped to shreds before firing on them as they retreat. Raptors and Chaos Space Marines also fall victim due to their poor morale and health. Rangers with Guardians are an excellent counter to an early Raptor harass.
Rangers lose their effectiveness in later tiers against Chaos due to Khorne Berserkers and their T3 elites, all of which are morale-immune. Eldar
Rangers are essential in mirror matches as they provide a method to engage the opposing player's Rangers and will break Dark Reapers, allowing your Guardians to do their task. Be aware of your opponent using their Guardians to tie your Rangers in melee combat. If this happens, engage them in melee combat while your squads focus-fire them. Rangers deal superior melee damage to Guardians and the sword-wielding Warlock does little to tip the engagement in their favour. Later on, Rangers are used to pick at the other player's elite units such as Warp Spiders and Fire Dragons which are very difficult to counter due to their durability.Orks
It is wise to forgo Ranger Infiltration in this matchup or even Rangers full-stop due to the presence of the Mek. His charge bonus and detection will keep Rangers in check indefinitely while Stormboyz and Shootas engage your other units. Waaagh Banners will also detect Rangers and render harassment incredibly difficult.Imperial Guard
Rangers should be brought out after two squads of Dark Reapers in this matchup due to the Command Squad's detection and speed. Pulling Rangers out first will allow your opponent to neutralise them entirely and give them time to mass and tech. Bringing them out after establishing a decent damage-dealing force will allow them to engage both the IG player's buildings and infantry.Tau
An incredibly difficult matchup for the Eldar player. Rangers are necessary to shut down the opponent's Vespids and to break Fire Warrior squads if the Vespids are shaken off so that Dark Reapers and the Farseer can engage. Later on, Pathfinders will render them nearly useless due to the ridiculous damage and range of Fire Warrior squads when sight is provided.Necrons
Rangers can be counterproductive in this matchup due to Scarab detection and Wraiths. A straight 3 squad Reaper mass is preferable.Dark Eldar
Hellions are able to neutralise Rangers using their Tracking Device ability while Jetbikes finish them off. Once again, a Reaper mass is a better option as Mandrakes can be harassed more effectively at the beginning due to the relative ease of massing Reaper squads after the stone has been bought. Rangers are almost essential in T3 as Warp Beasts and extremely dangerous unless broken.Sisters of Battle
Missionaries make Rangers difficult to use early on so infiltration is best avoided. Rangers and Dark Reapers should be used to neutralise either a Seraphim harassment or a flamer mass, should the opponent choose to use one for whatever reason. Countering Seraphim harassment can be very difficult on many maps but with Fleet of Foot and a degree of accurate prediction, Eldar tend to have an easier time than most races. Later on, Rangers are made relatively ineffective due to Seraphims' and their T2 ability to make the entire SoB army morale-immune.Discuss this guide in the Eldar Strategy Forum.