Retro 3d Graphics cards.

Collecting old computer hardware is a strange hobby. You spend hours pouring over eBay/shopgoodwill/other second hand markets looking for items that interest you. When collecting retro hardware, different people look for different things.
For me, I like old Windows 95/98 machines and I’m mostly interested in hardware from the late 90s to 2000. There were many options back then. The competing standards the different cards supported had died. Direct 3d and OpenGL were the standards developers used. Glide support was still desired, so some PC makers to offered both an Nvidia/ATi card AND a 3dfx Voodoo 2 card.

If you want to make a old retro system, and you don't want to think too hard about what card to get: Find any Geforce card from the 256 to the FX. If the system has a AGP slot, it will work. You can find them for cheap on eBay, since the MX line was the go to card for OEMs.

But if you want to make your life harder, well let's get into it:

Add In Cards.

Cards like the 3dfx Voodoo or the Power VR cards. Voodoo cards are in high demand right now. The Voodoo/Voodoo II cards plug into a free PCI slot on the motherboard, so adding one to a newer system gives you Glide compatibility with older titles on a newer system. You can add a Voodoo II to a fast PIII or Athlon system and still be able to play Mechwarrior 2 how it was first released. (The Voodoo 1 works best with Pentium/II/K6 systems. It has issues with the faster FSB of later Slot A systems).
Pairing them with a TNT2 or GeForce 256/2 card makes for a great Y2K build.

AGP Cards.

AGP cards are usually a 2d/3d card (many CAD cards were 2d). Win98 Direct 3d and OpenGL acceleration. There’s a large variety of cards and performance in this category. Let's break down the more popular brands and cards

Nvidia Chips: Riva 128, Riva TNT and TNT2, and Geforce 256 SDR/DDR/2.
3dfx Chips: Voodoo Banshee, 3, Velocity 100.
ATi: Rage 128, Rage Fury/Maxx
S3: Savage 3 and 4
Power VR: Series 3

Interesting Cards (for collecting)

ATI Rage Fury Maxx: dual GPUs on one card. This card was not as massive as you would think a 2 gpu card would be.

Nvidia Geforce SDR: The “low end” Geforce 256. It did not come with DDR memory, but SDR found on the previous gen.

Power VR cards: All of them are interesting/collectable. The Kyro cards in particular, since its the same tech as in the Dreamcast.

3dfx Voodoo Rush: a weird Frankentien’s Monster of a card. 3dfx put a 2d chipset and connected it to their 3d chipset. It could do 2d/3d graphics, but in reality it worked the same way having a add-in 3d card worked. (no windowed 3d)

Happy collecting!