Of all the lenses Fujifilm makes for the X system, they do not make a fisheye and they don't have one on the roadmap for future manufacture. Now, fisheyes are mostly gimmick lenses to me and I do not use them real often but they are very wide and they can be corrected in Lr or Ps to be rectilinear if you prefer to not go with the bowed, curved effect they provide. That curved effect though, can be useful in certain shots, again from a creative perspective. Used, for instance, in an outdoor shot of the sun in a cityscape or landscape and you can get a cool starburst effect which may make an image even better. Your mileage and all that. But its something you should at least try before deciding its not for you. Buy, rent or borrow.
I finally decided to go ahead and buy one for the Fuji system. I had a Sigma fisheye for my full frame Nikon system when it was my kit. It was used a handful of times. When it comes to Fuji though, you are going to have to look at something Chinese and of those the Rokinon/Samyang company produces the best optics at the best price. They produce a LOT of very good lenses at some great price points. Their (FUJI) lenses are all manual focus and they transmit no data via the lens contacts but its not really even an issue. It's so wide with such a huge depth of field, set it to 3 ft and shoot to infinity with everything in between pretty much in focus. I bought the Samyang which is the EXACT same thing as the Rokinon version, built in the exact same factory but the Samyang version here stateside is $30 cheaper. $30 is $30 so hey, its the way I went. Other reviewers have mentioned you may need to return a copy or two to get a good one. Mine was packaged well and functioned perfect out of the box. No problems. Its a tiny lens compared to the Fuji glass. Its pretty well made and has a built in lens hood which is really just a protector for the bulbous front glass element.
I'm not going to get into any real technical data since its on the web and easy to find. I'll show a couple of images though, one is with the straight fisheye and the other is with the standard Samyang 8mm profile applied, standard for Lightroom. Understand it could be further refined and altered using the Transform panel.
As you can see, its got a curved effect and the closer you are to a subject the more pronounced it will be. You can eliminate the curvature effect and further fix it up if you seek a really wide shot. You can do a lot of creative things with it and if it weren't rainy, cold and snow showery out, I would show some better images. But you get the idea. Oh, you do need to be careful with composition because its really easy to get your feet in a shot.
For $269 shipped, its a keeper for those times it will be handy. Sort of a gimmick but then so are multiple exposures, gels with lights, and lots of other things regularly used in image making. Whats one more?