It also depends on if you are using the character as an Antagonists of a Raider. It also depends on what cards you are using in conjunction with the weapon. I don't think there is a clear idea of what the best weapons are, but there is a clear idea of what the worst weapons are. I will add to that list:
Harec: all of Harecs weapons are good, none of them suck and have different uses and strengths.
Shae: I don't know enough and have never really played her. Perhaps someone more experienced with her could comment.
Doldren: His sub machine gun sucks. Don't use it. Default and Bloody Marry are better.
Iune: Her default sucks. All 3 of her other weapons is when she really begins as a unique character. Sigh and Vortex are good as support weapons when you are a raider. Wisdom is great as an Antagonists and crowd clearing.
Alicia: All her guns suck, except Rock & Roll, which is overpowered right now. Smoking Daisy can be good in very skillful hands, but R&R makes all her other guns obsolete.
Laoht: Dragee and Bubblegum suck, especially bubblegum. Just use Popcorns or Cookie.
H.I.V.E.: All her guns are good, none of them really suck.
Rak: No idea, don't even own him yet. Someone else may be able to answer this.
Lycus: I actually never really played him. I heard Peper Pot is the best, but I've never heard of any of his guns sucking.
Hans: I also, surprisingly, never really played Hans. But I've never heard of any of his guns sucking. Maybe someone else could comment.
Mika: Same, I'm not a big Hades Division fan. Perhaps someone else can comment.
Schneider: Again, Hades Division. No idea.
Konstantin: Non of his guns suck, but his best is clearly Tolchock.
Kuzman: Default is the weakist, but I wouldn't say it sucks. All of his guns are useful in some way.
Ginebra: There are only two guns anyone ever use with her, Schleuder or Javalin. The other two are too TOO situational to be consistently useful. To me they suck.