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.
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.
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