OK a "brief" unit explanation. And then I will post my armylist that beat the crap out of my Imperial Guard player buddy. I massacred his entire army, not even a single model survived/escaped. I will post his IG army list aswell just for comparison.
HQ
Farseer HQ unit: very potent psyker has 3 kickasspowers that I tend to use in any game.
1 Doom = target any enemy unit within 24" and get re-roll to wound on those poor sods
2 Guide = target a friendly unit within 6" and they get re-roll to hit
3 Mind War = target ANY enemy MODEL
within 18" and then both players roll Ld test. If psyker wins the enemy looses as many wounds as he lost pts in the Ld test. Without any save at all allowed so its very useful on enemy HQ and special weapon soldiers/sgts with power fist ans so on.
Avatar HQ unit : A must have, bolstering any Eldar within 12" range to become FEARLESS just like him, he has 4 wounds, he is probably the best CC unit in the universe with his ws10 and he also has a melta weapon with 12"
Autarch HQ unit: If you have both the Avatar and Farseer then he is pretty useless. He is a like a Exarch with all stats 1+. You mau buy lots of gear for him though from all aspect warriors. And his main use is to be fielded in Recon missions due to his 1+ to Reserves capability.
Warlocks: They need to be bought in 3-10 squad and then you may add them to whatever unit you wish. The warlock has a nice CC weapon that allways wounds on 2 with no saves allowed and gets S9+D6 for armour penetration something to surprise the enemy armour with. Also they get one permanent psychic power. The most usefull is one that adds 1+ to I and WS, and another that is like a flamer template w S5 Ap4. Warlocks may also buy a power so that they may guide Wraithlords and Wraithguard warriors so that these units dont get the penalty rolling 1D6 every turn and if they score a 1 they are useless for the entire turn just standing there.
TROOPS
Guardians = Well in this edition of Eldar they suck and are not needed, they are guardsmen with ws/bs 3 and 5+ Sv and their main drawback is that their shuriken catapults only have range 12". They may field one support platform within the squad but its not worth taking up one troop slot with these.
Dire Avengers: Now this is the real troop choice. They have WS/BS 4 and a 4+ Sv. Not to mention that the exarch has some powers that add to their potential. This dudes can walk 6" fire their shuriken catapults up to 18" and still charge and beat the snot out of any enemy that still stands in their way. If you can field as many as you can of these!
Rangers: Now this is the cream of the regular infantry you can buy for troop choice. I ALLWAYS uppgrade them for a small fee to PATHFINDERS. Pathfinders get 2+ to their cover, and their shots become AP1 on a 5+ to HIT. This means that you can shot any enemy unit to hell or get pinning! I pinned 3 necron units with 2 squads of this boys and that saved the day.
Eldar Jet Bike: This are just like Eldar Guardians but airborne. I can only see this unit work if you get at least 6-12. Every 3rd Jet Bike can get a Shuriken cannon and THAT is a light tank killer with its S6 assault 3.
Wave Serpent: Here we have a "transport" with as much armour as the falcon/fireprism BUT also with a force field , degrading any attacks against front and side armour with S8+ to S8! And you get to choose a twinlinked turret weapon and a shuriken cannon! I allways use the brightlance, with BS3 you will get a reroll if you miss the first time. Also it transports 12 men to the front.
FAST ATTACK
VYPERS: Ok if your real heavy support units and all else fail you still have this super swift unit. Fit them with Eldar missile launchers (krak S8 Ap2 or Plasma S4 AP4 pinning) or a brightlance and flank those tanks! They are really cheap but get 2-3 so you can make a difference every turn. They only have BS3 and are open topped. Still on a good day they will shoot even a Demolisher to scrap metal. If you have 3 of them and no other Fast attack choices make them 3 seperate units.
Swooping Warhawks: I have a full squad of this babies. OK this unit is quite difficult to master and are quite frail but have their potential. First of all they may deep strike, AND RE-DEEP strike. Meaning thaty you can deep strike them at least 3 times per game if you wish. Every time they deep strike they drop a "grenade pack" being a large blast ANYWHERE on the table with a scatter possibility. Its quite wealk but it still can kill T3 units with 5+ Sv. Every Hawk is fitted with a Eldar version of the lasgun, but they are 24" Assault 2. The Exarch has some other version but I ussualy go for the 24" Assault 6 pinning Sunrifle. This units should just fly around as far away from the enemy as possible and shoot at them from full range, or be used to kill off mortar squads, ratlings and such annoying units. They also have Haywire grenades taht make short work of any armour with the nice stats of 1D6 result [1= nothing, 2-5 glancing hit, 6 penetrating] If you have 5-10 haywire grenades you WILL destroy that tank.
Shining Spears: Eldar equivalent to IG Rough Riders, they carry lances with 12" range and may use them as power weapons in CC. I don't own this unit and from what I have read and heard they are not worth 1 Fast attack slot.
Warp Spiders: Another VERY fast unit. All members of the squad have 3+ Sv and S6 Assault 2 12" weapons. They are meant to deepstrike shoot the crap out of small elite units or the rear of a tank and then make a second jump in the assault phase much like the Tau, and jump into safety. Looking Forward to use them
ELITE
Howling Banshes: Some say this is the Eldar CC unit no1. They have I10 on the assault and 4 power weapon attacks/member of the squad. Should anyone survive their onslaught they will probably die due to their low T3 and 4+Sv. However they may fleet of foot like most Eldar so they can get in fast moving 12-18" / turn.
Striking Scorpions: The Heavy version of a CC unit. THey have 3+ Save but their thick armour has a drawback - they cant fleet of foot. So they should be transported close to the enemy and attack from there. They have better armour and better S than the Banshees. Wielding Scorpion swords they get S4. But they doesn't count as having power weapons so its the players choice what to field.
Harlequin Troupe: Now we are talking CC! They only have 5+ invulnerable save but boy do they know how to kick @ss!. A unit of 10 Harlequins with all special characters like troupe master and shadowseer get 46 Attacks with I7 on the assault WITH rending possibility if you equip them with Harlequins kiss!! They also have 2 Fusion pistols (meltapistols) and 1 Shuriken cannon within the squad. If the Shadowseer is added to the squad the enemy must roll 2D6x2 to check if they can spot the Harlequins because of the Shadowseer conceiling powers.
Fire Dragons: Tankbusters extraordinare. They are also good at killing off special characters with their meltaguns. A squad of 6 including a Exarch with a Firepike (meltagun 18") and "tankhunters" only cost 131pts. Not bad for something that may fleet of foot, and kill 1 tank per turn! Add them to the Falcon tank and transport them across the battlefield up to your enemies lines and wreck his armour.
Wraithguard: Ok they cost quite a lot and only have 1 wound and only 12" weapons, they are blind so they need a warlock to guide them with "wraithsight" But, they have T6, 3+ Sv, and their weapons kill ANYONE with no armour save allowed, just sucks them into the warp and they are gone !
HEAVY SUPPORT
Eldar War Walkers: The bane of armour and T3 enemies alike. Mount scatter laser on 3 warwalkers and you have 24 S6 shots, with Guide and Doom from the farseer the enemy will be in trouble. Also the Scatter lasers S6 and swift movement of the Walkers makes them good flanking units to killlight armour. Their low AP makes them quite useless against Space Marine armies unless you arm them with the more expensive choices like Starcannon, Eldar Missile launcher or Brightlance. I only pick them with Scatter lasers against T3 armies though.
Dark Reapers: I nicked them "Dark r@pers" since that is what they do with their 48" Heavy 2 S5 Ap3 attacks. Bane of necrons, space marine, chaos, withhunters and other heavy armoured armies. With Doom and Guide, and an Exarch with fast shot adding 1+ shot to their shooting phase and the Exarch missile launcher being S4 Ap3 heavy 2 small blast. You will kill 1 squad of space marines per turn. Just keep them faaaar away from the enemy and it will be happy times for the Eldar.
Falcon: In the Codex they say its the main battle tank. But I wouldn't agree. I would say medium tank/transport for 6 models. Its quite good, can pack some firepower and get a half squad up to the fron. But has BS3 so its not the best accuracy for brighlances, keep the Pulselaser (S8 Ap2) and this tank becomes very cheap.
Fire Prism: A truly magnificent vehicle, it has 2 fire modes, generating small blast S9 AP2 or a large blast S5 AP4. It uses BS4 to hit targets so no scatter dice for this bad@ss gun needed!
It is very fast and hits hard. Still you have to consider what foe you will be facing or if you have enough transports to take a Fire Prism over a Falcon. The price is almost the same for both, Fire Prism is slightly cheaper. If you have 2 Wave Serpents and already have warwalkers/wraithlord/dark reapers filling 2 heavy support slots take the Fire Prism.
Support Weapon Battery: I dont think this is a good idea at all, including 1-3 Heavy support platform it takes up one valueable Heavy Support slot, so unless its a small 500pts game avoid taking them. Cheap and pack a lot of punch but are not mobile, swift and flexible as the other heavy support choices.
Wraithlord: Never leave the Craftworld without him! This should be any Eldar players FIRST heavy support to be bought and then used in 40k games. A truly awesome creature that needs a warlock to be 100% sure that you wont get him useless on a D6 of 1, a risk you will take each turn. What the Wraithlord has, T8 = almost nothing can harm him, 2 flamers on each arm, BS4 + up to 2 Heavy weapons that may fire in the same turn, and 3+ Save with 3 wounds. Now , I allways pick 2 Flamers, 1 Shuriken cannon (assault = shoot + beat the cr@p out of anything that survives the initial BBQ) and one brightlance/eldar missile launcher to take down enemy armour. If you have both the Avatar and the Wraithlord in the army they WILL soak up a LOT of fire power leaving your main army to take out the enemy.