Custom item icon for a 3D weapon

its normal. in mcreator the item appear as a 2D model. but in game its 3D. just make sure that u choose ur weapon model.

First, make sure that all of your planned behavour of the item is finished (because you will have to lock that). Then head to the file tree and find: {your mod name}/Resources (Gradle)/assets/{your mod name}/textures/items and there add your texture. Then browse again for: {your mod name}/Resources (Gradle)/assets/{your mod name}/models/item/{your item name}.json and rewrite it to this: 

{
 "parent": "minecraft:item/generated",
 "textures": {
  "layer0": "{your mod name}:items/{your texture name}"
 }
}

If it does not work tehn please reply.

It doesn't seem to work in new releases, there is a way to do it in 2020.5 too?