For me it’s hard drives… I’ve saved every single one I came across that still works, even 20GB slowpokes from a couple old PC’s and Netbooks that went to the local electronics recycling center. I also buy new drives when I have a serious use case (such as my local backups that need more space every couple of years).
I have a few hoarded 2.5" SATA drives, all with good, Linux-compatible USB enclosures. I either buy Vantec enclosures, or make damn sure the enclosure has a known-to-be-rock-stable-in-Linux controller chip, such as the JMicron JMS578 or JMS456.
I was hoarding too many Sandisk and Samsung MicroSD cards (which were only 1/3 the price as I normally paid, when I was in Malaysia) so gave them away as gifts.
When I say hoarding, I’m referring to buying multiple of something, and you just store them up, not actually actively using them in production. The media that you store backups on sort of don’t count, as they are in production (albeit, are mostly at rest).
I have even some IDE disks still in use (250 + 320 GB) once a week for max 1 hour They are part of my 9 IDE disks, from 425 MB to 320 GB. I have 2 loud SCSI disks (18 + 36 GB) and a 20 GB IDE 2.5" disk. A number of floppy drives.
DDR memory sticks 266, 400 MHz; SDRAM. Two 400 MHz DDR sticks are still in use
Two Analogue PCI TV Cards one for EU and one for US TV signals.
AGP Video Cards 2, 8. 32, 256 GB, a classic PCI video card of 128 GB and a 1 GB PCIe GeForce 8400GS (GT218) with a defective mini-fan.
WordPerfect 5.1 plastic keyboard template with all shortcuts.
The used memory sticks and disks are part of my Pentium 4 Backup Server
I too hoarded a nicely Linux-compatible AGP video card, it was some sort of Asus Geforce card with a sweet 64MB of RAM, but it got lost in a past attic. It had a two-inch or so fan. Quite a few similar-era Linux-compatible treasures were also in that attic: like a U.S. Robotics 56K external serial modem. Also a rare Canon USB scanner which had no compatibility problems.
My fan was ~1" / 2.5 cm. It is stuck, the temps are still workable during normal operation around ~80+°C and it has a margin till 128°C. I used it in a 2008 HP dc5850 and I want to re-erect that PC in September. The PCIe 16x slot is on the bottom of the Motherboard and Tower, so I could glue a spare 80mm case fan on the bottom next to the card. Maybe I could even connect a spare laptop cpu fan to the card with e.g. zip ties
If you hoard things, you always find some crazy solution.
All I have left of my hoard are a Summer 2001 Indigo iMac, a FW 800 G4 PowerMac, an external hardware serial 56k modem, and a Linux-libre compatible Conexant 56k USB modem. The modems are there just in case the broadband internet infrastructure collapses. (We are talking about hoarding tech, not about logical, realistic and not crazy reasoning.) So I guess turn of the century Macintosh computers are my hoard. Like a dragon, I do sleep on them. No I don’t.
I’m not a hoarder, I’m more a collector and besides a 486DX66 (own build in 1993) and a Philips P3105 XT clone, both stored in a cabinet and last tried and working in 2014, I still use;
The remains of a 2003 HP D530 SFF now mounted in a even older Compaq Evo Tower with a Windows 98 SE activation sticker
It has a Pentium 4 HT (3.0GHz); 2 GB DDR (400MHz) and two IDE HDDs (3.5"; 250 & 320 GB) and two SATA-1 HDDs (2.5"; 2 x 320 GB), in total 1.21 TB. It boots and runs 32-bits FreeBSD 13.0-RC4 on OpenZFS 2.0 and I use it since June 2019 as my main backup server for the weekly backups. It is powered on for ~1 hour/week. So I age faster than this Pentium system
A 2008 HP dc5850 with a Phenom II X4 B97 (4 x 3.2 GHz); 8 GB DDR2 (800MHz) and only one slow 80 GB HDD, so not used due to a lack of useful disk storage.
HP Elitebook 8460p with an i5-2520m; 8 GB DDR3 (1333 MHz) and currently with a very slow 160 GB HDD, my 1 TB SSHD started collecting bad sectors in the hundreds per day during last week. It now runs Ubuntu 21.04 on ZFS and the 2 GB memory cache makes it somewhat workable after booting (> 2 minutes) and first program loads.
Own build from April 2019 with a Ryzen 3 2200G; 16 GB DDR4 (3000 MHz); 512 GB nvme-SSD (3200/2300 MB/s); 128 GB sata-SSD (545 MB/s) as cache for the 1 TB and 500 GB HDDs. My main desktop with Host OS Ubuntu 21.04 with persistent L2ARC (SSD cache) and ~50 VMs (Ubuntu 4.10, 6.06 LTS to 20.04 LTS and 21.04 Beta; Windows 1.04 to 10 and many others)
I’m impressed by the great L2ARC performance, VM boot times are very close to those of the nvme-SSD.
Note that the 160 GB HDD currently in the Elitebook is one of the reasons that I switched to Linux; in 2008 in dual boot and after retirement on 1-1-11 completely. That HDD (35/40 MB/s) came with a new laptop in 2008 with Windows Vista. I hated that Vista laptop, but after switching to a 320 GB HDD, that was twice as fast and after two service packs Vista did become really workable, almost like Windows 7.