It's interesting how many people in this thread have similar loadouts to mine, for example always carrying a sword/other melee weapon, even if not playing as a melee build.
Anyway, for me it's usually:
1 - sword or other melee weapon
2 - pickaxe
3 - axe
4 - strongest, usually ranged weapon
5 - anothor weapon with a more situational use
6 and 7 - random stuff, usually fishing rods, summons or more weapons. I used to carry health potions here before I knew about the hotkey lol
8 - random common blocks, usually stone or dirt
9 - torches
0 - magic mirror
Also, funny related story: My oldest character from, like, 2013 that I still use from time to time has sunflowers in his hotbar. When I started playing I was terrified of the corruption spreading and with my limited knowledge of the game I thought sunflowers were the best way to stop it. I thought they were super important so I put a stack of them in my hotbar and for some reason I never removed them. It's been so long now that removing them would not only just feel weird, but they're also a memento of a simpler time, when corruption spread was my biggest worry.