for me, i think worst is not the objectively worst, but the stuff i bought that i just don't use. it may be pretty good sounding, but if i don't use it it's a complete waste of money. hence:
sony XM4s: never paired to the right device, have to find the device to disconnect it, find the other device i want to connect it to, rinse and repeat. it turns out i hate bluetooth, i mean, ANC is great, it sounds good with EQ and is tolerable without, but my god if i turn it on, it automatically connects to my ipad and then i can't find the ipad for 15 minutes, it's not particularly convenient, which bluetooth is supposed to be. result is that i just use the sonata BHD or an apple dongle or something and leave it sitting. would be good for gaming, but the latency is way too high, sooooo..
sony ex-800s: sound good, but don't sound as good as er4xrs despite what crinacle thinks. also turns out that IEMs that don't isolate and leak aren't that useful for me because i use them in the office (ok i haven't been to the office in a year, but you get the idea). maybe XM4s will find their way into the office.. the ex-800s will be making their way to the for sale pile.
fiio BTR1K: only 50$ (or less, i can't remember) and just meant to add bluetooth functionality to some headphones for a trip, but i would bet it performs pretty poorly and i'd just sprung for the btr5 (there was no qudelix then), it probably wouldn't just be sitting. have i mentioned that i just can't get into bluetooth?
worst: too many frickin cables! i don't mean audiophile cables either, but just all the different cables you need to connect things in all the different lengths that keep the spaghetti in check. at one point a couple years ago i just started counting up all the different usb, rca and 3.5mm cables i had into varieties with identical function because they were overflowing multiple ikea boxes and started tossing the lengths i would never use. the worst part is that you NEVER HAVE THE EXACT CABLE YOU NEED! it's one of those universal mysteries like socks disappearing in the dryer.
also worst: i have too many single board computers. they just started collecting from research and other projects and now i have a box of them. none of them were expensive, and almost all of them have served some purpose, but now that the project is over, do i really need 4 beagleboard xms? no, the answer is no. could i run volumio on all of them? yes. would it do me any good? no, no, it wouldn't. except for the pi4s for octoprint and the duet 3 sbc, they're all getting donated to a high school/makerspace before i leave.