I still have a USB to PS2 adapter, and I KNOW I'll find a use for it, someday.
But that's not what I'm here to talk about. I'm here to talk about odds and ends, accessories that may have come bundled with other stuff, but you found a use for.
For example, I found a Logitech 501888-0000 in the shed at the house we used to rent. Now my wireless adapter looks like the antenna on a Volkswagen:
https://www.amazon.com/New-Original-Logitech-External-Stand/dp/B0088WD3II/ref=pd_lpo_sbs_147_t_2?_encoding=UTF8&psc=1&refRID=E7F9GM1KVA1JEZQ6ZGBSWoo, 12 bucks? I hope mine never craps out.
The USB extender I plug my hub into came with a giveaway 256 mb MP3 player.
My cousin stole it, it had my 128kbps dead milkmen collection.
But the vestigal electronic I used today was the HDMI extender cable that came with my much maligned Chromecast. Mom got her current TV for free behind goodwill, which was a score because 1) it was the same model as the one that died on her. 2) It had the stand, unlike the dead one, 3) The remote is interchangeable, and most importantly 4) The dang thing still goes for $600, despite being an older Vizio.
The one downside is that the HDMI port seems to have been pushed in by impotent rage of prior owner, so nothing really works. I noticed the shiny metal bit of the HDMI extender was a bit longer than the standard HDMI interface, so I gave it a shot and hooked it up to a blu-ray player. Sure as poo, IT WORKED!
Also, Vizios apparently let you rename the interfaces, and the HDMI interface is named "golly" so that gave me a chuckle.