I seem to remember seeing a plugin for this somewhere, but I can't find one when searching for infinite or unlimited. Any item added to the inventory would be boosted to its maximum stack size, and stay that way until dropped.
CommandBook is the only plugin I use und know whitch creates infinite stacks of items. But you have to give you every single stick by yourself. this will give you an infinite stack of obsidian: Code: /i 49 -1 You can use it as long as you want. Even if you drop it and pick it up it's infinite. I don't know what happens if someone else picks up the infinite stack. Good luck on your search
@RobotGymnast Also Creative+ and SimpleAntiGrief, but that isn't their main purpose (well it sort of is with C+), so it is buggy, and has unnecessary stuff in it as well.
