Posting my design ideas for each weapon:
Instant Iaido - Real-life samurai art of drawing a katana and attacking in one graceful motion. This isn't meant to replace Jarate in non-medieval, but should be a decent melee companion for Snipers who still keep their SMG. In medieval, you have to be careful how you use it and when you draw it to attack, to avoid being one-shot by melee attacks.
Nobunaga no Nobara - "Nobunaga's Wild Rose" - it was the best alliteration-name in Japanese I could come up with. This weapon is basically my old Olympian Torch idea - bonus movement speed and capture rate while wielded - with a softer downside. I think it's a little too powerful, but I don't plan on nerfing it. I might add another interesting downside to it. In the mean time, it should be useful in medieval and off it, giving you 5% more speed (which translates to +20 HU/s on the scout) and an extra capture rating for a managable tradeoff.
Problem Solver - Still trying to solve this problem: What should it do. It has the funny attribute of explosive ammunition in the mean time. It's a demopan for the Engineer! What more could you want?
Incense Inhaler - Steak Sandvich for Medic. Or so I intended. The "forced melee" attribute on it isn't working. People are complaining that medics are using this to have fun in non-medieval and should be healing them. I personally thing people should be able to do what they want, and if they aren't healing, it's pretty likely removing this weapon won't make them heal. I have an interesting heal mechanic in place for this medigun that I will be adding in the short term, so healing can take place in medieval mode (or off it).
Scrap Collector - A passive bonus for the engineer. Meant to make him more durable in melee combat. That is its soul purpose. It's a bit narrow in design, I could see it being useful in non-medieval though. It uses an unsuable wrangler because Valve attributes do not work if a weapon is made "inactive" like the flame retardant suit. The flame retardant suit's fire resistance is actually a script Mecha made.
Flagrant Flintlock - Precision-based weapon for the spy. Not much more to say here. There is currently an exploit which gives this weapon potentially no reload time and no head-shot cooldown, but that's because of Valve! I can't do anything about it. You can do the same with the Ambassador. They have yet to fix it. If someone is abusing this weapon or that glitch in general, please report it on the forums. And do not teach others how to perform the glitch, please.
Ye Olde Handcannone - The kickback for the Engineer. It wasn't working out for the scout, but my original intention was to make it for the Engineer. I have a big change for it coming, so expect it to evolve some. Right now, it should be situationally useful for teleporting backwards around the battlefield.
Critsmourne the Lifestealer - Just meant to be a joking reference to Warcraft's Frostmourne. Though it should be a practical weapon in its own right. The scout has many methods to generate mini-crits - this is another way.
Ol Benjamin - Area of effect weapon for the Engineer. It's meant to pack quite a punch in medieval, though I've nerfed it a little bit since release. In non-medieval, it could be used just like the shortcircuit, providing a basic alternative: Do you want more sticky-destroying power? Or more emergency close-ranged damage. I'm considering putting a weak cloak-drain effect on it, but maybe I should consider something more interesting.
Antique-Artillery - A vanilla-y ranged weapon for the soldier. Meant to make his play more varied in medieval and be a seductive alternative to the buff banner.
I have a heavy primary coming soon. I think I'll spoil the basic idea of it: It fires cannon balls.