I haz idea :3 rebelling grass! When you randomly swing your sword around, each grass you hit has like 1/20 chance to pop out and hit you for a small amount of damage that grows larger over time so you have to deal with it, or stop killing grass, which in turn stops mushroom and daybloom and stuff growth so u have to clear them XD
the grass has 1000 defense like dungeon guardian and has ~5 hp, different biome grass has different damage/hp and different debuffs, they drop grass banners and some copper coins, when hardmode comes on the chance for rebellious grass is increased to like 1/10 and they are buffed a lot (to stay relevant)