I like the pulsar line for single player PvE crowd control, and I'm trying to match a sword to it. Being Elemental it would make a combuster redundant. It pretty much leaves me with either shadow or piercing weapons. A piercing weapon would probably be a better match, considering what I face, but I'm not really fond of how they handle. Actually, none of them really grab me, so I can't really decide what to put with the Polaris. Any suggestions? Thanks.
Sword to go with Polaris
You'll probably want a Gran Faust. It has a chance to curse with the second hit of the combo and has good damage and wide range. The charge is useless compared to the Acheron but the Acheron's charge is mainly used for long range (as ironic as it sounds) and you already have a Polaris for that. For example if you're against a Jelly/Gremlin/Construct/Beast then you can combo swing the enemy to knock them back (and possible curse them) and then unleash a Polaris storm on them. Hope I helped.
My big thing against piercing swords is that you can't really use them 100%. Most of the time, because they push you into the fray, they're only good for the first strike. Also, their charge attacks are not very useful (maybe BTB is...). Lastly, the get a lot of benefit from AT, but I don't use AT, so there's another plus I'm losing.
I was thinking GF at one point. With all the crowd control I get from Polaris, I can afford a slower sword. The uselessness of the charge kinda puts me off, but it might be my best bet.
What about a bomb? Maybe I should consider going that route?
The Toothpicks are very good to have once you learn to use them well. Shield-cancelling the first strike, plus some ASI (Swiftstrike Buckler) gives you great DPS. Also the best weapon for Greavers. The Final Flourish charge is perfectly usable, and good for taking down Wolvers when used in combination with something like a Shivermist/Stagger or a vortex bomb. As for AT, just toggle it on when you want to use the full combo.
If you want a shadow sword instead, I'd probably say Acheron. O.o Gran Faust takes getting used to because of how slow it is and using the full combo can be risky. When your Pulsar knocks enemies back it gives you some time to set up an Acheron charge.
When you bunch enemies in a corner together you probably want a weapon with a very wide swing. Like people said above, Gran Faust works very well. I don't know if you are a 2slot player or a 4slot player so I cannot recommend anything personally.
Cold Iron Vanguisher
Jalovec
Acheron
Gran Faust
I personally don't like polaris spammers (Mostly because I use 100% swords and the knockback is annoying). But since it's so knocky-backy, you should probably go with swords with tons of knockback:
Leviathan Blade
Sudaruska (Jalvotec freezes on the second hit / charge, leaving you vunerable for the opponent to strike.)
Furious Flamberge (Even though it's not used much, it is better than a Fearless Rigadoon because most things that are weak to piercing aren't fire resistant.)
That-One-Hammer (You know the one)
Archeron.
Since I don't use a Polaris (I use a neutralizer!), I wouldn't know for sure. These weapon choices are only guesses.
I have heard many posters say that they don't like how the piercing swords handle. Ultimately it's up to you, but I recommend that you practice with them, to give them a fair chance. They really are a powerful tool against the nastiest monster family (fiends). Of course, they're also good against the easiest monster family (beasts), but that's not worth much. They're also pretty good against gremlins, because they have decent speed and reach, and the first swing is wide. And that's relevant to you, because your gun is weak against gremlins.
If you still don't want a piercing sword, then I agree that you want a shadow sword. My detailed sword guide can help you choose between Gran Faust and Acheron.