Editing Warhammer 40,000/9th Edition Tactics/Space Marines (section)

===Melee Weapons===

*'''Astartes Chainsword:''' SU, '''AP-1''', D1, +1A. As of 9E, all Space Marine chainswords get AP-1 on top of the extra attack, making them even better against lightly armoured hordes while also giving them a little utility against tougher foes. 
*'''Lightning Claws:''' SU AP-2 D1, re-roll wound rolls and +1A per claw. This will outperform all other D1 melee weapons against any target (except T8-9 with a 2+ or 3+, where the power sword wins, but why are you picking D1 weapons for those?). Your best bet for mulching single-wound hordes.
**+1A for one claw, +2A for two claws, so two claws usually cost twice as much as one for a tiny fraction of the benefit; anything forced to take two claws is often easily overshadowed by something with the choice to take only one. 
*'''Power Weapons:''' Each type of power weapon has its own profile now, so pick the right one for the situation. Unless you have the option for a lightning claw, then you should always take that instead.  All of these come in Force flavours as well for Librarians, which changes from D1 to Dd3, making it marginally worse than the reliable D2 available on Master-Crafted versions.
**'''Power Axe:''' S+2, AP-2, D1. Outperforms the sword against T3 and T5 models, since you wound them on a 2+ and 3+ respectively, compare to the swords 3+ and 4+. 
**'''Power Maul/Power Lance:''' S+3 AP-1 D1. This is the one you want least; boosting you to S7 isn't that much more useful than the axe's S6 and you lose a point of AP in the process. If you want to bash units with T6+, just pay the 5pts and grab the powerfist. 
**'''Power Sword:''' S+1, AP-3, D1. Best against targets that rely on armour saves over toughness to shrug off hits, and particularly good if you have access to re-rolling wounds. 
*'''Powerfist:''' Sx2, AP-3, D2, -1 to hit rolls. Good against everything, cost-effective, and very common to find.
*'''Chainfist:''' Sx2, AP-4, Dd3, -1 to hit rolls and becomes D3 against Vehicles. A Terminator-only weapon. Marginally better than a powerfist against other highly-armoured models that lack an invulnerable save, strictly better against Vehicles, and has a 1/3 chance of offing a Plague Marine in one go by shredding through their -1 D Disgustingly Resilient. Costs the same as a powerfist, so trading the fist's reliable damage for better AP could be worth it.
*'''Thunder Hammer:''' Sx2, AP-2, D3, -1 to hit rolls. A powerfist that trades one point of AP for an extra point of damage. The extra damage could mean the difference between one-shotting a Custodian Guard/Aggressor/Terminator or getting a guardian spear/powerfist in the face. When you have a thunder hammer/storm shield-Captain with Jump Pack, every enemy model begins to look like a nail. BUT, at typically twice the cost of a powerfist, it's not worth ditching up to three extra special or heavy weapons just to squeeze out a few extra points of damage. Still quite viable on everything that isn't a Character at least, so feel free to spam with Terminators or Vanguards.
*'''Relic Blade:''' S+3, AP-3, D2. Available to Vanguard Veteran Sergeants and Captains. It has a good comparison to the power fist, but the two models that can take a relic blade can also take a thunder hammer. 
** Ignoring S bonuses or wound-roll buffs, the powerfists bumps you to S8, whereas this takes you to S7. This only matters against T4, T7, and T8 targets, as you go from wounding on a 2+/3+/4+ respectively to a 3+/4+/5+. 
** With hit roll modifiers capped at +/-1, attack units with inbuilt "enemy attacks suffer -1 to hit rolls" isn't so debilitating, again making the fist/hammer the better choice.