Dev boards for different microcontroller and fpga platforms. Also UART to USB adapters because I can never find one when I need one and just end up ordering more.
Anything else I can buy bricks and mortar without much hassle.
I feel like if I stocked up, I'd then feel more tempted to shop as my supplies dwindle. I also find that if I have a large supply of something, I use it faster than expected.
That said, there's a few replacement parts of things I use regularly that I have no idea where I'd shop for something compatible physically. Things like produce savers for my fridge and filters for my air purifier
Just the things currently on my shopping list. A CPU fan, a network card, some exterior lights for my house... There are no items that I buy online repeatedly.