Revisiting the topic of Specialization and Eldar, I give you a unit of Striking Scorpions.
One of only two aspects geared for melee combat, and even then specialized towards specific prey.
Thanks to their mandiblasters, the Striking Scorpions truly excel in the number of attacks they can generate in assault. While lacking the power weapons of their melee-sisters the Banshees, they do benefit from a very welcome +1 to Strength given from their Scorpion Chainswords.
These guys specialize in taking out high numbers with low armour (orks, Imperial Guard, gaunts, Dark Eldar, etc.).
On top of that awesomeness, they have a 3+ armour save, perfect for warding off those high number of attacks mob/swarms will likely through back at you.
Can anyone guess what it is about them that I like the most? Eh?
You can equip their Exarch with the ability to allow the entire unit to Infiltrate. That's the sweet spot.
Speaking of Exarchs...
Never satisfied with just one option, I made all three Exarch variants for my Striking Scorpions. The Chainsaber'd Exarch was a small conversion. He has the usual right handed Exarch Saber that comes with him (sword+claw has same sword) and the left hand was the arm from the Biting Blade, but with a normal Scorpion's sword attached (and cleaned up with a little Green Stuff). While reading through the entry, I found that the Chainsabers option comes with "gauntlet-mounted twin-linked Shuriken Pistols." Well damn. I fished some spare bits out of my bitz box for the two pistols, and Green Stuff'd a wrist-connection to look similar to what's on the Dire Avengers sprue for their Exarch. I think he came out looking pretty damn good.
You get a couple options here:
Chainsabers
Scorpion Chainsword + Power Claw (shuriken catapult incorporated)
Biting Blade
Similar to the Dire Avengers' Exarch choices, each one will gear you to excel in a differrent way.
When taking an Exarch with your Scorpion squad, you equip him in a manner to best suit the role you want your Scorpions to achieve. Also, each equipment set is better against different enemies. Low-med toughness and low-no armor? Chainsabers all the way. These guys allow you to reroll failed rolls to hit. Combine that with the twin-linked shuriken pistols and he greatly bolsters the effectiveness of the Scorpions. The Chainsabers set is great for low armor horde armies. Swarms of gaunts (even 'stealers, though you'll take heavy losses as well) mobs of Orks, Imperial Guard, Fire Warriors, other Eldar.
Sword+Claw. This is great against high armor enemies (though really, aim your Banshees at them), but because of the sword he becomes the best choice for versatility. He can do nearly anything, where the other two are a bit specialized. Something to be said for him also ... Gauntlet mounted Shuriken. He can fire that off and use the Claw same turn.
Facing high toughness, med-low armor? Biting Blade. This set sacrifices one attack compared to the others, but you get +1 Strength for each successive hit. Note that you already count as having a S4 due to the Blade itself. 1 hit? S5. Get 2 hits? They both hit at S6. Three hits? S7. Did you get all 4 hits when on the charge? You lucky sunuvabetch, that's 4 hits at S8. But, still no armor penetration.
This makes him viable against high Toughness enemies. Be careful, the rest of the Scorpions are still Strength 4 ... and won't be able to efficiently follow in what you're trying to accomplish with the Exarch's potential for 6 or more Strength. Those high Toughness models are better taken care of with firepower, like from Warp Spiders, or Wraithguard, or even the Rangers. Better to aim the Scorpions at a juicier target: mobs of cannon-fodder troops.
