A thread in which we try to allay the fears of big damn robots ruining everyone's game. A few things to remember that a few people have gotten confused about or simply forgotten:
1. Gargantuan Creatures automatically have Feel No Pain, but not It Will Not Die. I myself was guilty of thinking that this was a thing until recently.
2. The Wraithknight does not get an Invulnerable *and* a ranged Destroyer weapon - it has to choose between ranged Destroyer or the Shield.
3. While it does have 12" move unhindered by cover for being a Jump Gargantuan Creature and has Move Through Cover, it does not ignore the Initiative Penalty for charging through terrain with it's large base.
4. Gargantuan Creatures are only wounded on 6s by Poison and Sniper weapons, but any other fixed value wounding will still work; Deathmarks, Fleshbane, Agonisers if they still work how they did in the old book; 'Unstoppable' does not give you blanket defence from fixed to wound rolls. Also, they're not quite immune to Instant Death; they just take large amounts of wounds instead of rolling over and dying straight away. Sure, it's not as good, but if you can Instant Death then do so. Works for Fantasy, works for 40k.
5. While Eldar can have a considerable number of psychic dice, they don't have access to psychic defence from Psychic Hoods, and so getting Maledictions through is surprisingly easy. Gargantuans are no longer immune to psychic powers, if you're a grognard like me who remembers that being a thing.
Adepta Sororitas: You know the drill - throw mountains of Str8 AP1 at the problem. If it goes away, gravy. If it doesn't, you die horribly. Business as usual.
Astra Militarum: Lascannons with Fire On My Target/Bring It Down, Vendettas, the Paskisher, Plasma Vets if you're really stuck. Huge potential from Psychic Powers; Misfortune and FRFSRF or a charge will give a WK a really hard time, Enfeeble from Wyrdvanes can make it a lot more manageable etc.
Blood Angels: Similar to Sisters, fire lots of Meltas but you can also bring Lascannons and Stormravens with their Meltas and Missiles to mix it up a bit. You can try and torrent an already-wounded one in combat due to Str5 on the charge. Power Fists and their ilk going to Str9 on the charge can do some considerable damage. Access to Divination means you can get Misfortune and do that old trick, albeit to a lesser extent because Bolters aren't as numerous as Lasguns (on the other hand, it also works in melee, so charging in with Death Company with Astorath to give them Shred or something similar could be an amusing counter).
Chaos Space Marines: Try and rush it with Maulerfiends? Blastmaster spam? Fuck, I don't know. Sorry guys. Black Mace Daemon Prince will fuck up a Wraithknight royally but you're gonna have to land, not die, and still be able to catch it afterwards. Still, a lot of sass points if you actually do it.
Chaos Daemons: Daemonettes are the name of the game here, but most of the Greater Daemons can at least chip a few wounds off. Plaguebearers only wound on 6s, but that's better than not wounding at all. Use Malefic, summon up a bunch of Daemonettes, profit. Tarpit with Grimoire-augmented units and hope for bad Stomp rolls.
Dark Angels: Hammernators and Deathwing Knights. Rad Grenade Launchers and/or Misfortune from your Divination access followed by Bolters R Us or Plasma Talons from your Bikers/LRCs and Black Knights. Charging it with Corvus Hammers is stupid enough that it might actually work. Rad Grenades are gonna be pretty central to the plan here since they're a really nice debuff (double points if you get an Allied Enfeeble to make it T6).
Dark Eldar: Poison only wounding on 6s is a bummer, but when you're firing 120 shots a turn you can still push some through. Use those bajillion Dark Lances you have to chip away at it. Charge with Caltrop Reavers for sass points. Grotesques with Flesh Gauntlets would be hilarious if you rolled lucky.
Eldar: What the fuck are you doing reading this? Bladestorm, Warp Spiders and Wraith-guys, you're super fine.
Grey Knights: Daemonhammers are your go-to here, probably on Dreadknights for the mobility (WS5 and Sanctuary means you can even have a go at the Sword and Board Wraithknights if you feel gutsy), but your entire army works. Hammerhand up (Halberds being useful, who'd have thought!?) and Force away. Psycannons will eventually chip wounds away but probably not worth doing. Vortex of Doom if that's a thing. Soul Glaive will make them have a big sad with Hammerhand up.
Harlequins: Fog of Dreams, Laugh of Sorrows, Mask of Secrets; Armour of Misery, Dominate and Psychic Shriek from Allied dudes. Do your usual leadership shenanigans and laugh at the silly Craftworlders.
Imperial Knights: If they have the Wraithcannons, charge at the earliest opportunity. If they have the Suncannon, laugh in the Eldar player's face and make him try and charge you through cover. If they have the Sword and Board, try and stick to cover to make him strike at I1 so you can punk him before he swings and does it to you. The one time you bring a Magaera and it gets a wound through with it's Rad-Cleanser is an occasion worthy of song. Still not a real faction.
Khorne Daemonkin: Bloodthirsters are probably all you've got, although gunning for lucky 6s on Bloodletters is a reasonable plan if you can reach melee. If Skulltaker still does his Brutal Legend decapitation thing, worth a shot.
Necrons: Lychguard with Scythes (make sure you pop that Solar Staff when you get out of the Night Scythe so you don't die before you hit combat), Tesla Destructors, massed Warriors, Flayed Ones if you can get them Furious Charge from Zahndrekh, Deathmarks using their Interception thing to get Fleshbane, Wraiths, massed Warrior fire if you need to take the last wound or two off.
Orks: Klaws, Lootas, Klaws, Mega-Kannons, Klaws, Big Choppas, Klaws, Tankbustas. Charge with Bully Boyz and wreck it with Killsaws (sure, you'll lose some to the WK's swings, but considering StrD is actually less deadly for Meganobz than Str10 is, you're not going to lose a whole squad since you're WS5 and you don't need many Str9 AP2 attacks to make a WK have a sad). Shokk Attack Guns if you have loaded dice.
Space Marines: Grav Centurions, Hammernators, Lysander, Biker Chapter Master, Misfortune/Enfeeble from Tiggy/Loth, Grav-Guns on Bikes or in Pods. Grav makes you probably the second or third best army set for killing a WK after Eldar themselves.
Space Wolves: Thunderwolf Cavalry is probably the way to go. Wraithknight will struggle with Storm Shields without rolling lucky 6s and you can mess them up pretty good with massed Rending and Str10 Power Fists. Charge it with Blizzard Shield Dreadnoughts if that works for a laugh.
Tau: Monster Hunter HYMP and massed Railguns/Fusion Blasters. Storm of Fire and Fireblade with some Markerlights if you've stopped giving a shit. You really, really aren't going to struggle.
Tyranids: Anything with a lot of attacks and Rending Claws, Toxicrene for a funny and reasonably legit counter, massed Implant Attack if you feel lucky, Boneswords if you can roll 6s. Paroxysm taking it down to WS1 BS1 is amusing. Swarmlord with some Tyrant Guard to take the D for him should might do it if you can get Furious Charge or Preferred Enemy or something. Gargoyles with Blinding Venom.