For me, it’s the Teva Pinners I recently purchased for cheap at jensonusa.com. They are a huge improvement, grip- and comfort-wise, over the shoes I was wearing while riding. I’m also thankful for my Qu-Ax Cross 29. It’s the unicycle I ride the most by far. Additionally, my scarred shins and calves are thankful for leg armor.
Hoppley Thanksgiving Day.
The seat.
It would be most uncomfortable without it. :D:D:D
I really appreciate having a wheel on my unicycle. lol!
Ibuprofen.
I’d say the unicycle “accessory” I’m most thankful for is this forum. It inspired me, motivated me, and connected me to an amazing group of people.
If we need to be more tangible in the reply to this I would say the following parts that were made available to me for the cost of only shipping. This is really to underscore the original sentiment; that this is a generous community of ideas, as well as equipment.
KH/Onza hub and cranks: Eric (Sask)
KH24 Rim: Nurse Ben
Rail Adapter: Spencer Hochberg
Maggie pads: Brycer
Thank you to everyone who makes this community so successful.
Jerry
+1 
Ahhhhhh, we love you man.
Ditto jtrops!
Great answer!
I am thankful for unicycle.com and all the various unicycles and parts I can choose from and browse all the time. Of course, the vast amount of knowledge and helpful people on the forums have been invaluable to my unicycle learning.
To echo Jtrops’s post, I’m also very thankful for this forum. I’ve met some great people through here, and am more motivated than ever by some (most notably Aspen Mike). Any time I have a question, even if it’s dumb, someone is there to help me out, and for that I’m grateful.
As far as unicycles go, I’m most thankful for my 700c and Muni. Both pretty much do it all for me (so far).
As far as equipment goes, I’m not sure what I’m most thankful for. The flattened seat has certainly caused a ripple in the community though.
I’m thankful for my old Schwinn Giraffe, the first unicycle I ever owned (I had borrowed ones before that one). More recently, my SilvaCycles custom Schlumpf 36" is my most-used unicycle, and has taken me very far.
Parts:
KH saddles. Thanks Kris, our asses’ hats are off to you! People who never experienced our sport before your line of saddles were available have no idea. Also I love my two pairs of 5.10 shoes.
Other:
+1 on that. It’s the reason I was able to really get back into uncycling after all these years. The “new” saddles have probably made the sport more feasible for a lot more people. It used to be your ass would kill you after a 5+ mile jaunt. I mean really kill you. ~5 miles used to seem like 20 now.
I’m also thankful for my new 137mm Spirit cranks. Those things really rock. I also love my KH20, Oracle 24, 36 and…well all my unis and everything related to them! Hillbilly gloves have saved my hands and wrists so many times and…
A lot to be thankful for.
Like others I am quite thankful for the community, but if I had to pick one thing it would be the development of the 36" wheel for the kind of riding it promotes.
I am thankful for gravity, without which all of this would be meaningless.
But isn’t that true for nearly every sport? It’s hard to think of any that don’t need gravity to work as intended. It will be interesting when we have large enough habitats in orbit (or on the Moon) where totally new sports will be able to develop…
I’m thankfull for the crutches I borrow from my friend Jack. I need them every august, because that’s when I start to feel in control on my muni rides. Every year it turns out that I’m not.
I agree with John Foss about the KH saddle. I started riding when I was a kid in the 1970s. When I returned to the sport (to ride with my kids) the KH saddle on my then newly-acquired Onza Muni just blew me away. The tushy comfort now available has allowed us old guys to keep riding. Without those saddles, I don’t think you would see all us 50+ year old guys on this forum. Would UDC even be economically viable without all those sales to Unigeezer, Foss, etc.???
+1
I’m trying to understand your response. Does that somehow make it not true or less true for unicycling? Wouldn’t it have been equally illuminating to have written, “but without gravity rivers wouldn’t flow?”
I’m grateful for the Miyata air seats, Gazzaloddi tires, Reeder handles, GB4 seatposts, Roach shin guards, Profile hubs, and Hunter frames. Guess what all these have in common… 
without gravity the outer layer of the Earth would float into space along with the lawn chairs. Then we’d float away from the Sun into cold darkness.
Truly, gravity makes unicycling possible.