Jon’s Useless Mod is a special mod that users want to install even the author admits it is useless, maybe in order to be funny by making a statement which is clearly false. There are remarkable things needed to pay attention to play this mod well.
The fact this mod comes with a config file where you can adjust the settings on blocks and items should be enough to tell you it isn’t actually useless like the author claims. Jon’s Useless Mod introduces a special Dave mob that will follow players and literally beat them to death if they happen to pull out some of the custom, useless food items available in the mod. Much of this content can be found in the Useless Dimension, which is a custom biome one must build a portal to travel to, a lot like the Nether or the End in vanilla Minecraft.
There are a couple of custom useless achievements to earn as well, but unlike the rest of the content in this mod these actually are useless, since they don’t do anything for the player. The author of Jon’s Useless Mod notes that thanks to some interactions between Minecraft 1.8 and the Waila add-on, there might be some flickering or loss of visuals in the custom dimension. If you want to avoid this, just disable Waila if you have it. You can totally ignore this warning if you don’t use Waila anyhow.
for Minecraft 1.8
Credit: Jon – Original Thread on CursForge