I have been waiting for this! I'm not sure exactly how big the changes can be ( I included smaller reworks as well. I know, they aren't likely to be put in game but I still wanted to share my ideas ) but here are all my ideas that could work:
[Small weapon reworks]
{Melee}
•Yoyos should be more unique, the only one that's unique is terrarian which is an endgame weapon. Examples: mini explosions on impact with cascade, small fire aura around hel-fire, yelets shoots stingers once a second, eye of cthulhu charging at enemies etc
•Night's edge could have a unique mechanic of increasing its damage the longer you deal damage with it ( requires being close to the enemies for longer ). It would stack up to +8% damage, depletes over time. It's definitely a pretty good item but having this mechanic makes this legendary weapon even cooler
•Excalibur: the same thing as night's edge above but with increasing melee speed instead
•Lightsabers could reflect lasers and have increased knockback. That makes them more viable and unique
•All boomerangs should pierce at least once and some should have special effects:
•Spore boomerang creates a spore cloud on hit
•Ice boomerang can inflict frostburn
•Flamarang has a fire aura, damage increased to 35
{Ranged}
•quad-barrel shotgun could work kinda like before the rework. For me, it should still shoot 4 projectiles ( since it has "quad" in the name ) and damage could be increased to ( slightly less than at the start ). The fact that it is now post-skeletron + reduced usetime changes a lot so it shouldn't have been changed that much
•Blood rain bow shoots more arrows ( it's really hard to hit enemies, this bow should be actually worth getting ), damage increased to 17, crit chance to 9%
•Bone arrows break after they pierce ( similiar to crystal bullets ). That makes them a more viable and unique ammo
Silver bullets deal more damage to werewolfs ( based on legends )
{Magic}
•Blood thorn's projectiles should be longer, damage increased to 39, ignores 5 enemy defense points. I don't see a use for this item, it's currently neither good for regular enemies or bosses
{Summon}
•Pirates from pirate staff should be way more mobile, damage is increased to and can deal contant damage when flying. They are basically worthless, every other hardmode minion outclasses them
•Optic staff could ignores 5 enemy defense
[Stat changes]
•Storm spear: dmg from 12 to 15
•Light disc: dmg from 57 to 68
•Thunder zapper: dmg from 12 to 20
•Weather pain: dmg from 13 to 16
•Neetle burst: dmg from 35 to 38
Wasp gun: dmg from 31 to 33, mana cost from 10 to 8
[Accesories]
•Putrid scent upgrades should give 3% damage increase so they have a use in singleplayer. 3% per accesory isn't that much and it would make the upgrades worth using
•Lucky horseshoe and it's upgrades could allow for holding "down" button to fall faster ( there are almost no items which allow faster fall speed )
•It would be really nice if toolbox, toolbelt and ancient chisel could be combined into something like "ancient tool set". Wearing them individually just takes so much accesory space and this suggestion would make it a cool accesory for building
[Enemies]
•World feeder's head should inflict cursed inferno since it drops cursed flames
•Dreadnautilus should charge at you slower/at a bigger angle. In my opinion it's his most difficult attack since you need insane movement speed or weird movement to dodge it. I have seen a mod that changes him into a boss and it also included that rework
•Giant digger and Giant fungi bulb should have their own banner instead of sharing it with their pre-hardmode versions ( just like what happened to moss hornets in 1.4 )
•New sprite for chaos elemental. My own idea attached below!
•New sprite for banners of: moth, some mummies, chaos elemental ( from my suggestion above )
•Required enemies killed to remove pillar shield changed to 75 (100 on expert+)
[Armor]
•Obsidian armor slightly nerfed: range increase from 50% to 45%, speed increase from 35% to 30% ( this makes bee armor nad early hardmode armors more viable )
•Bee armor: set bonus also adds 1 bonus minion (+3 In total), dmg increase on set bonus reduced from 10% to 7%
•Shroomite armor: ( a bigger but necessary change imo ) it's way too similiar to vortex set and I don't see any use in incresing damage at the cost of literally not moving. Here's my idea: it could slowly spawn short-lasting spores around you, touching them slightly increases your stats and the effect stacks to for example +20% damage +15% crit strike chance, +10% increased knockback, +2 hp regen ( works as a stacking buff like boosters from nebula armor )
[Other]
•Electrified tooltip changed from "you cannot move" to "don't move!" ( current one makes no sense )
•Furniture from angler's quests should have a higher chance to be a bonus reward if you have done enough quests
Hopefully I didn't forget about anything important and autocorrect didn't mess something up. Thanks for all your work!