I have tons of spare parts.
I think around 10-ish Pentium-MMX 233's or so and a couple other CPU's I have a lifetime supply of spare parts. And around 9 of the same Chaintech 440BX boards with 4 SDRAM slots (I'm not sure all of them are in working condition though, but most of them should be. They are a few different revisions though).
I have I think 8 or 9 S3 Virge's, but most are of different makes.
I even have 2 of the same AT cases made by Commodore 😁 (they were Pentium 60's, still got the two Socket 4 boards as well).
And 5+ A7V133's, though I didn't find those particularly special, but all were for free anyway. No ISA slots though and no official Palomino support, so the use of those boards is rather limited.
I happened to have checked in my attic yesterday for those IBM clicky keyboards, apparently I only have two of those, one is missing it's sticker with serial numer and such and the other has had a couple of it's keys replaced with non-matching keys (I found it this way). Dunno of the 2 keyboards are in working condition though, they are rather old (the other was from around 1994-ish).
2 GA-6OXET Tualatin boards I remember having bought from the UK (I was the only bidder, they were sold as scrap but both posted fine and one is in one of my rigs even. Was a lucky shot).
I know I have multiple ASUS Tualatin boards (both several of the TUV4X and TUSL2-C variants) and I should have around 6 Tualatin 1400S chips along with plenty Tualerons of almost all speed grades (Not all Tualerons I have spare parts of though).
2x Radeon 9600 256MB made by Sapphire. These are identical except that one has some kind of extra sound chip I never bothered to use and the other one is missing it.
I think I had 2 of those ASUS 430HX AT boards (both v3.1 or so, the variant with the tag RAM pre-installed), but I do remember one had a broken memory clip or something (memory worked fine in the board though) and I also had at least two FIC AP-2000-something boards? (the ones with the VIA Socket 7 chipset which could run with single memory modules installed instead of never being able to boot with memory installed in pairs).
I should also have 2 Intel D815EEA (not supporting Tualatins though), the first one was broken (Socket lever was broken at the base, no way to glue it back so I replaced it with an identical Socket lever from a dead Socket A board, lifting up the top half of the entire Socket, replacing the lever and "clicking" the top of the socket back, the part that slides forwards and backwards when you install and uninstall the CPU) and it worked! ...except that I found out the board I had repaired had a dead floppy controller. Still build a rig around it though which served me for many years. The second one I got years later which I never really used but it did POST I think.
Of course I have enough Coppermine 1000's (I think all revisions which are 133MHz FSB, don't own any 100MHz FSB 1GHz Coppermines though).
Several Athlon Thunderbird 1400's (133MHz FSB ones again), also have many of Intel's and AMD's stock coolers as spares, some identical and some with slight changes, some with somewhat different heat sinks but identical mounting clips.
I don't know from top of my head, but I have 5+ Live! sound cards (some 5.0's and some 5.1's, something like that).
And I do know that I had at least 1 or 2 matching pairs of Voodoo 2's (have 9 in total).
All my Rendition 2100's are made by Diamond (5 or 6 in total, they only differ in the sticker I think) and I also have the Viper 550 (TNT) and Viper 770 (TNT2) twice, along with a single Viper 770 Ultra.
A couple Geforce 2 cards I have identical copies of I think.
The funny thing is that even though I have tons of sound cards, except for the Live!'s, virtually all of them are different (except maybe for a 1320 or 1350-something? , but I think one of them had a broken resistor or something).
I do know I have 2 ASUS P2B's, but both are totally different revisions (one supports Coppermines and the other doesn't)
I have some other CPU's as spares, but they aren't really significant I think (like a Sempron 2400+ or so)
One of my more interesting spares is a VC820 board, as one is a production model with 2 RDRAM slots and the other an engineering sample board with 3 RDRAM slots (the board with 3 RDRAM slots is hopelessly unstable though, impossible to finish installing Windows ME before it starts to bluescreen, the other boards installed it without significant issues).
This all is from top of my head (where do I keep al this info stored 🤣! )
edit: I forgot I also bought 10 of those 400MHz ATZ 3+ chips from that German seller, tested every single one of them one by one with success! 😁
At first he didn't want to sell to me (as I was abroad, even though The Netherlands and Germany are neighboring countries) but I persuaded him into selling me the chips anyway 😁
Also have a couple other Super 7 AMD mobiles with spares, but less then 10.
And iirc I also had the s370 1.0GHz or 1.2GHz VIA chip with a single spare (I wasn't sure both of them posted though, but the board did have some kind of issue)