So this list is in NO particular order, but relies a lot on Forge World rules. And in case you couldn't deduce from the title, it is entirely for Space Marines. Sorry... BUT several of these things can apply to all Astartes codicies. The list is kinda long, but there are some rarely seen AMAZING options here IMO.
1- War of Murder: This is 20 pts or 40 on a super heavy. It gives the vehicle you give it to Monster Hunter, which allows rerolls to wound against Monstrous Creatues (pg 168, BRB). Note, Gargantuans ARE MC per the BRB pg 70. So rerolling to wound against all those high T creatures is critical. So Land Raiders, LR Redeemers, Predator Annihilators and Vindicators are all great choices for this.
2- Battle of Sarosh: This is 30 points or 60 on super heavies. Once a game you grant a vehicle Skyfire, Interceptor, Tank Hunters and Night Vision. So generally best against Flyers, the Skyfire/Interceptor helps against any Flying MC and Tank Hunters can take on tough to crack super heavies. This to me seems great for a Relic Sicaran and Predators.
3- Schism of Mars: 25 points or 50 for a super heavy. It gives the vehicle Tank Hunters and +1 BS against enemies with the Daemonforge rules. As well it ignores Haywire on a 4+. This guy provides nice defensive abilities, is a good price IMO, and is great for hunting Knights and the like. I myself am putting this on a Sicaran, but also seems good for Land Raiders, Predators and Vindicators.
Predators: Killshot Special Rule. If you have 3 Preds, they all gain Monster and Tank Hunter. If you are going "Take all comers" with this style, Autocannon turrets with Lascannon Sponsons can be usefull, but it you KNOW you will be facing a lot of big guys, all Las-cannons may be required. Alternatively, they are still good ran cheaply with all autos and no sponsons.
Vindicators: Linebreaker Bombardment Special Rule. With 3 of these bad boys, you can get a nice apocalyptic blast on one of the vehicles firing with the ignores cover special rule. And it is S10 AP2. So combine that with one of the three legacies above and you have something truly brutal. The really cool thing is that RaW, only one tank fires, so really you only need to give one of them a Legacy. Alternatively you could give one the War of Murder and one the Schism of Mars. This makes you adaptable in any situation if you don't know what your opponent with bring as you can switch between who the firer is. A really great way to make an already good thing AMAZING.
FORMATIONS
There is one formation of note here. The Land Raider Spearhead. 3 Land Raiders that not only ignore shaken, stunned, immobilised and weapon destroyed results within 6" of each other, they also gain the ability to reroll to wound/penetrate Gargantuan Creatures and Super Heavies. And 4 HP a piece at AV 14 is still hard for even D weapons to remove easily.
CHAPTER TACTICS
So FW has its own set of Chapter Tactics. There is really only one to take note of IMO for the purposes of this article
"All models with Chapter Tactics (Red Hunters) have the Adamantium Will special rule. In addition, once per game at the beginning of any one player turn, the controlling player may declare that a number of their units with Chapter Tactics (Red Hunters), including Dreadnoughts, equal to the number of the turn being played will have one of the following special rules, chosen by the controlling player, until the beginning of their next turn. For example, if the protocols are activated in Turn 3, then three units may choose a single special rule from the following to apply:
• Counter-attack
• Monster Hunter
• Tank Hunters
• Hatred
• Skyfire
• Interceptor
By this Seal: When using the Allies Matrix, all models in the Red Hunters detachment count units from Codex: Grey Knights and Codex: Adepta Sororitas as Battle Brothers so long as an Inquisitor is also present in the army"
EDIT- Realized I read "By this seal" wrong. Fixed my understanding now.
As you can see from the rules, this is great to form a Take All Comers list, as it is the ultimate in tactical flexibility IMO. Centurions and Devastators in particular can benefit from several of these options. It is definitely something worth considering giving to a small detachment or accompanying formation (Skyhammer Annihilation Force mayhaps?). I have also discussed in the past how it is great for Deathwatch Space Marines.
ADD ON TOP OF THAT Everything gets Adamantium Will. They just have it. Talk about some strong psychic defense. AND Battle Brothers with GK or SoB!!! How nice is that!
CHARACTERS
And to round out the list, there are 2 Forge World Characters
BUT lets look at what Vale really brings:
• Unstoppable Advance- All Rhinos, Razorbacks and Land Raiders in a primary detachment commanded by Tarnus Vale gain an Invulnerable save of 5+ against glancing hits.
• Stubborn
• Tank Hunters
• Master Gunner- Any friendly vehicle with the sub-type (Tank) chosen from Codex: Space Marines or the Space Marine Siege Assault Vanguard army list in which Captain Vale is being transported gains the benefit of his Ballistic Skill (6!!!) and the Tank Hunters special rule.
• Storm of Fire Warlord Trait- grants rending to one unit w/in 12" a turn.
SO what does all the mean? Well a nice little defensive buff to all your transport, the ability to give out Rending every turn, AND turn a unit/transport he is in INTO a tank hunter unit. This can combine nicely with the War of Murder LoG on a Land Raider Reedemer that he has mounted up in. With his BS6 giving you a 2+/6+ to hit and an ability to reroll to wound AND penetrate makes this a solid choice. Alternatively you can put him into a devastator squad and give them Tank Hunters. Pop a devastator doctrine (and even a tactical doctrine!) and watch the destruction unfold.
"Any unit with this special rule that does not move in the Movement phase of their turn may choose to gain the Rending special rule when firing in the Shooting phase of that turn with boltguns, combi-weapons fired as boltguns or bolt pistols. When using this rule, all boltguns, combi-weapons used as boltguns and bolt pistols fired are counted as being Heavy 1 weapons instead of Rapid Fire or Pistol type weapons for that turn."
So this can be pretty nice for taking out some vehicles and MCs with massed fire. Here is also what he brings though.
• Shrouded
• Infiltrate, Isolate, Destroy: If an army includes Lias Issodon its controlling player may select a single enemy unit, Monstrous Creature or vehicle that has been deployed onto the table. After any Scout redeployments have been made, but before the game begins, the chosen unit suffers D6+3 wounds with no AP value if a squad or Monstrous Creature, distributed as shooting hits (assume the attack has originated from the closest unit in Issodon’s force). If the target is a vehicle, it suffers D3 rolls on the Haywire table instead.
• Cunning Strategist: Whilst Lias Issodon is alive, the army may re-roll any Reserve rolls made (failed or successful). In addition, the opposing army has a -1 modifier to all Reserves rolls.
• Master of Ambush Warlord Trait from the BRB.
SO the really important thing there is the Infiltrate, Isolate, Destroy rule. D6+3 AUTO wounds means it averages 6-7 wounds BEFORE THE GAME BEGINS. Now apply this to these new crazy T9 creatures (Tau Supremacy Suit). Even with a 2+ save, he should fail 1-2 AND CAN fail more. That is really nice, to start the game. And d3 Haywire attacks vs vehicles, which means an average of 2 HP GONE right away. Imagine doing that to a knight. Just GONE. And possibly even worse results with a penetrating hit.
So I haven't even TOUCHED on all the possible combos, but I am sure there are some CRAZY ones out there. I love the idea of the 3 Vindicators with a mix of Mars and Murder LoG for the flexibility that offers.