This is where you show how old you are.... I will point out some of these upgrades were freebies / swaps
2D:
Western Digital WD90C31 (technically ISA, integrated with motherboard)
Trident 8900D ISA
S3 Vision 864 VLB
S3 Vision 968 PCI
Videologic Grafixstar 600 (Tseng ET6000) PCI.... eventually paired with a...
PowerVR PCX2 PCI (3D has entered the chat)
S3 Savage4 AGP (which I actually had very few issues with)
Nvidia TNT2 Pro AGP
Geforce DDR AGP
Radeon 9000 AGP
Radeon 9700 Pro AGP
Geforce 7600GT x2 (SLI - gave it a go... really not worth it... lesson learned)
Geforce 9600GT PCIe
Radeon 5770
Geforce GTX 570 **About when this thread was first created **
Geforce GTX 660 (not much of a performance upgrade, but boy was it cooler and quieter)
GTX Titan X
GTX 1080Ti
Gotta admit.... getting that itch... Radeon 7900GRE looks tempting although RT performance (which ultimately I'm not too bothered about) would be a problem later on....
On a side note: things I got to test and play about with when building things that were most memorable (things like Cirrus Logic and ATI Rage Mach2/64/Rage2/3D Pro really not that special):
Original IBM AT EGA 8-bit ISA card.. full length as well, Trident 8900C (first Trident card), S3 928 (first S3), S3 Trio64 PCI (might have actually been the first PCI graphics card I ever handled - it was so tiny), SiS 6326 (one and only SiS - wasn't bad in terms of compatibility but s l o w), S3 Savage (interesting, worked well when it worked - S3 MeTaL in Unreal was great), S3 Savage 2000 (the bugs...), S3 DeltaChrome (cheap, slow, but at least not buggy), 3Dfx Voodoo Banshee (not that good so got replaced with the following...), ATI Rage 128, ATI Rage Fury Maxx, Geforce 5200 (eeewww), Quadro FX5800 (basically a GTX280 with 4GB ECC RAM... A beast... Still have that on a shelf somewhere)