I have a couple ideas for items, but no way to actually build them.

Flamethrower: The Pyrophile's Proclivity
Based off of the design of the M-97
- 25% ammo
+50% afterburn duration
+10% afterburn damage

The Gunny Buns
A cosmetic item for the Soldier, featuring rolled up sleeves and the insignia of a gunnery sergeant. Based off of formal military dress, featuring home-made medals made of bottle caps and salami slices on the left breast.

The Saccharine Spade
Melee weapon for the Soldier, in the style of World War 1 trench raiding shovels. Barbed wire everywhere, even on the handle, serrated shovel 'blade'.
Each hit builds up "joy" similar to rage meter, alt-firing with full meter causes increased speed and defense
+10% swing speed
+Causes bleed damage on target
- Causes bleed damage on user
- Mini crits user when swing misses

Leatherneck Lacerator
A sword for the Demoman styled in the image of Officer's swords from the British Army. Killing the soldier with it grants 100% crit chance for five seconds. Kills on enemy Demoman activates "Marked for Death" debuff.