I think this would be very useful if you have 1 sword and a friend asks you for a sword.
You take any type of tool and put it in the middle of the crafting table.
For example: I use a diamond sword!
It will result in 2 half diamond swords.
Basically the diamond sword splits into 2.
Each half diamond sword deals less damage then a normal diamond sword and have less durability.
You can combine 2 half diamond swords in the crafting table to get a normal diamond sword however
if any of the half diamond swords are damaged even a little bit that damage will be added to the normal diamond sword.
This can be done with all tools.
If you want you can also split normal diamonds and iron ingots etc... into 2 and this:
D = Half Diamond S = Stick
It will result in 1 half diamond sword.
You can also combine 2 half diamonds to form a normal diamond.
Of course the same thing can be done with armors as well.
Just use the same method I told you with half tools.
put the (I will use iron chestplate) in the middle of the crafting table and you get 2 half iron chestplates.
When you wear this only half of your chest can be seen.
You can also make a half iron chestplate by crafting a normal iron chestplate with half iron ingots.
I'd rather make my friend a wood or stone sword than render my diamond sword worthless as a diamond sword. Half a chestplate would protect you how? How can a chestplate protect you if it doesn't cover you?