The Iron Hands are traditionally the First Founding Chapter that GW ignores. Their position is a bit better in this edition, as they have specific Chapter Tactics even if they are still missing out on named characters. The Iron Hands Chapter Tactics specialize in having the toughest Marines you can get without being dedicated to Papa Nurgle.
All Iron Hands Marines have 6+ Feel No Pain, unless they would get a better roll from another source such as a narthecium. This doesn’t sound like much, but it is used in addition to your armor save across your entire army. It will save a noticeable number of models in every game. Beyond this, all Characters and Vehicles have It Will Not Die. Your characters can be truly difficult to kill if equipped right, and the Iron Hands Chapter Master with shield eternal is probably the best version of that build. This rule also makes your vehicles more useful in the current game, as they can regenerate their lost hull points. Finally, Techmarines and Masters of the Forge add +1 to their repair rules, making vehicles even tougher in Iron Hands armies.
The Iron Hands lend themselves to a number of army designs. If you want to swarm the enemy with too many bodies for them to kill, the 6+ Feel No Pain will add quite a bit to your endurance. If you want to take a brutal Chapter Master to slug it out with the best the enemy has to offer, the Iron Hands offer the toughest you can find. Finally, if you want to run several heavy tanks, the Iron Hands are by far the best choice.
When I said Iron Hands didn’t have any special characters, I was technically right. However, their successors, the Sons of Medusa, have access to Iron Thane Vayland Cal of the Atropos War Clan. Cal has a very unusual statline due to his extensive bionics. He’s quite tough with S5, T6, and 3 wounds, though he only has 2 attacks. He’s well equipped with artificer armor, an iron halo, servo-harness and thunder hammer.
Vayland Cal brings a few useful special rules. He’s Fearless and Bulky, as well as acting as a Master of the Forge with the Lord of the Armory and Blessings of the Omnissiah special rules. He has the Angel of Death warlord trait, so he and his unit cause Fear. However, his big rule is Purge the Weak, which allows him to make up to three squads of Devastators T5 for the cost of 50 points and the ability to Run and Sweeping Advance. Even with a full squad, that’s really expensive. As a comparison, a Mark of Nurgle does the same thing for 3 points a model.