If you're interested in using the Gunsen war fan weapon, check this out. I've been using it and figuring out pros and cons.
Gunsen at a Glance
If you saw the Gunsen was released, you probably were interested like I was. Warfans have been a pretty interesting part of many video games i.e. Mortal Kombat's Kitana. Anyways, if you have any experience with MK you know that Kitana's warfans are fast, used for slashing and stabbing, and are throwable. The gunsen has very similar characteristics. It primarily deals slash damage and with it's only available stance it is in fact throwable through a combo.
Crafting the Gunsen
This section isn't going to be super in depth, as crafting isn't really the focus of the guide. The Gunsen's blueprint can be obtained through a clan's tenno lab. It isn't a very large project, with myself and one other person knocking out the funding in a day. The actual foundry blueprint isn't terrible either, but requires tellurium. Tellurium sucks because it only drops from archwing missions, with about the same rate as an Argon Crystal in the void. I would recomend doing submersable survival missions, as you can do them as your warframe and still get the drop.
I'm not going to list out the stats here, they're in the market and the lab. This is more of how it compares to other weapons I use. Like I previously stated, the Gunsen deals primarily slash damage. It's crit chances and status chances aren't terrible, around 20% each with barebones modding. They start out being really awkward to use, their reach isn't very good, their attack pretty low, and their speed variably slow. If you use the stance for them, and I cannot stress the usefulness of it enough, they become even more awkward early level. But I have a crit build with berserker, and they can be pretty insane to use.
Modding the Gunsen
First and foremost, be sure to pick up the stance mod. It's found on the plains and dropped by ghouls. It's supposed to be a rare drop, but I've already found 2, and I hardly ever see ghouls. The stance has some pretty good combos, and they can be achieved in a cheatsy way. Spamming block while you melee will end up give you a pretty solid three strike combo, and gives high damage and mobility. Your aerial attack is also really strong, any attack in the air will execute a "combo" that is similar to a spin attack. It's really fast, and the motion lasts over a pretty high distance. The slide attack with the stance is also really powerful, pretty much the same as the air.
Now, for your other mods you want to focus crits. Status works OK, but berserker is imperative to making Gunsen viable. The stance adds some strange motions to your standard hit chain, and berserker helps to bypass these weird rhytmes. The stance is meant to be acrobatic, explaining the need for motion to work right, but why even worry? Anyways, the standard crit mods are all fine, along with pressure point and reach to fix the early level issues.
From what you've seen so far you probably think there are a lot of faults to the Gunsen. And you are 100% correct.
Word of Warning
This is kind of a weird segway, but lets just go for it. The Gunsen has a ton of damage potential. However, these weapons are not a good new player weapon. They need mods or their slow speed and medium damage will rend them. Seasoned player like myself can make them work though, which is the case for pretty much any weapon. So, veterans, go nuts, the Gunsen are good. New players, give it a shot, but you'll need mods to get use out of them.