So when I started out, I used fun and unique and normal damage type weapons. Finding out that these were unappreciated, I decided to get all the hipster weapons. During this, I accumulated some not hipster weapons, here and there. Realising I now had most of the weapon archetypes, I decided that I would get one of each weapon-type-playstyle-thing. Now all I have left is to make a brandish, but I can't decide which one to make.
See, I can't decide between Glacius and Acheron. They will fill different niches. I don't own a shadow sword, but I do own some shadow guns and a shadow bomb. Ialmost always bomb slimes, and I don't like getting too close to gremlins, but maybe Acheron might change that. As for Glacius, it offers a rather interesting playstyle in lockdown. I do have other elemental swords though (DA and the hammer).
I rank the clockworks and lockdown as kind of equal in priority.
~Ethanol, Neutralizer's biggest fan.
You may or may not find detailed sword guide useful. It directly compares Acheron to Gran Faust and Glacius to Combuster, Voltedge, and the other elemental swords. I can't imagine not owning a shadow sword, but then I'm pretty into swords...
Except for the crowd-control properties of Voltedge and Glacius (which you can predict, because you know how shock and freeze work at this point I'm sure), all four 5-star Brandishes are pretty much identical in their play style. So it doesn't matter much.
Charging Acheron is a great way to deal with gremlins. Glacius' freeze is pretty fun, and may be useful in Lockdown, although I strongly prefer Combuster in the Clockworks.