cards that I own:
3dfx Voodoo 5 5500 AGP and Rendition Verite V1000L PCI (broken 🙁 )

any cards:
3dfx Voodoo 5 6000 AGP Rev 3700
Evans and Sutherland SimFusion 6500 😁 What a beast

Voodoo 5500 , good compatibility , 2D quality is great, and the performance is great for games up to 2001 or so (Im well aware of its deficiencies vs the GF2), it makes for a very nice Win9x era card.

I'm a fan of any card that uses the Tseng ET4000AX chipset, but if I could only choose one then it'd be my Geforce 2 Ultra, which does beautiful VGA / SVGA and of course is a handy 3D card too.

#1 Millenium G200
#2 G400 Max

Was a long term fan of Cirrus - my first was a 5428 VLB, my second a 5446 PCI, and also had a 5465 - and rather disappointed when a junkbox pick 5480 turned out to be dead

Tied between a Voodoo2/3 and PCX2.

Former for the filter and the gamma control which helped games to be visible on those CRTs, and the latter for the curiosities of its incapabilities and its unique 3d acceleration approach that even works through docking stations 😀

It was great to upgrade off the Voodoo though, no more filter of blurry game hell and hi-res 32-bit textures, can't deny that 😀. But then that's also around the time when it stopped being 'pick your quirky 3d card' and started being 'pick your generic accelerator with novelty feature and/or pick for pricerange/opengl performance'. Disappointingly the PowerVR KYRO was as generic as they come.

3Dfx Voodoo Graphics and Nvidia GeForce 3 Ti 200.

3Dfx Voodoo II, Matrox Mystique, Radeon 9800 series.

My favourites are Voodoo1, Ati Rage Fury Maxx and Matrox G400 Max.

Matrox Millenium II (Best Windows 3.x card, in my opinion)
Matrox Mystique + Rainbow Runner (above and ability to have a rainbow runner is cool)
Voodoo3 PCI (best overkill for an MMX build w/o AGP slot)
Voodoo2 in SLI (best pal for a GeForce 4 Ti)
Geforce 4 Ti (best pal for a Voodoo2 SLI)
Oak 067 512KB (sentimental reasons but also for its flexibility - TTL and analog connectors, switch selectable MDA/CGA/EGA/VGA modes, works on both 8 and 16 bit slots)

riva128zx and voodoo2

InfiniteReality. And from the common ones: the first Voodoo, because of its impact on the industry.

I can not choose one but here are some cards I own I really like.

S3 Trio 64. For a couple of years every system I built had one of these.
Voodoo Banshee. I really liked the Banshee and I still have my original one.
Geforce 3. Not a huge leap forward speed wise over what I had but a great card non the less.
Geforce 4 Ti 4600. It was expensive back then but I got one in a deal though the company where I worked.
Asus Geforce FX 5900 Ultra. I like that it can run at FX 5950 Ultra clocks but works with older drivers.
Geforce 6800 GT. I bought one when they were released and modified the BIOS to run at "Ultra" clocks.
ATI Radeon X850 XT(PE). I did not have one back then but they are great if somewhat noisy cards.
Geforce 7900 GTX. Its a great card with a great cooler.
ATI Radeon X1950 XTX. The fastest DX9 card with a single GPU.

Perhaps a bit modern but the Geforce 8800 GTX is a brutal video card.

Symmetric GLyder/TX Gold
nVidia GeForce FX 5800 Ultra
3DLabs Wildcat REALiZM 800

Love my voodoo 5 5500 AGP, Voodoo 3's are diamonds too. Great 2D and such individual looking 3D.
Always had a soft spot for the TNT & TNT2 cards too, even the M64, card quality can vary massively though, always found the creative labs cards very good.
Going for the total underdog here, but I am strangely fond of my Elitegroup SIS 315E 64mb card, it was cheap crap when new and I guess it still is, but one of the few ultra budget cards that cut the mustard, even the drivers are pretty acceptable, still have mine installed in an athlon box today, *almost* as good as GF2MX .
For modern-ish cards, I have to tip my hat to my ASUS Geforce GTX260 SP216, still pulls it weight today and runs lots of stuff maxxed out on my core 2 quad.
I'm pretty intrigued by the KYRO hercules 4000XT PCI I got recently but haven't gotten round to trying it out yet, tile based rendering is interesting tho(sure worked well on the iPhone).

By the era....

For early XT stuff and 286's I typically prefer the ATI VGA Wonder or Oak Technology 099 Chip cards with the EGA/VGA/CGA capabilities. I have three of these, though my 286 is currently using a 1MB ET4000 ISA card because I prefer the resolution and color depth I get when showing off Arachne (800X600 @16-bit color).

386/486 era, I on the ISA Side, ET4000 or Cirrus Logic chipsets because they are rather easy to get drivers for and have decent performance. Ditto VLB Local Bus though I also like my S3 809 1MB SVGA as well (want more DRAM to upgrade it to 2MB). For PCI 486's and early Pentiums I tend to prefer to use one of my old ATI Rage-II PCI cards because I have a big CD-ROM with every RAGE series driver on it so drivers are never an issue.

Anything PII/Pentium Pro or newer I usually just pick up some of those old XFX NVIDIA MX4000/400 PCI cards from the early 2000s, I had one of those in my Pentium Pro 200, and had a few different ones in my Pentium III, they were all great cards till I retired those boxes in the late 2000's. They were cheap too, and I could get them brand new at Wal-Mart for the price of a song when they were new.

The only graphics card I would never use again - the Trident TGUI-9440 PCI......e-god that card was awful, because the chipset automatically assumed a very very high refresh rate, so all of my CRT's would whine, scream, or say "graphics settings out of bounds" - ditto my LCD's. Also, the one mode I COULD get working reliably required a SVGA CRT with Multiscan, and the refresh rate was so high the gamma was so dark anything darker than a mildly dark shade of gray would turn up as pure black and blend into the darkend parts of the screen. I hated reinstalls with that thing, lots of registry hacking to get the refresh rates to work.

For me, It will probably be the first time I bought a ATi Card. A 128mb Hercules Radeon 9800 Pro. There is just something special about that card which blew all of Nvidia out of the water, the Geforce 5900/5950 just was not quick enough.
At the time I was just getting into On-line games with my DSL connection and was playing Unreal Tournament 2004.

Mmm, in chronological order of "i want this"

3D blaster VLB
M3D
Voodoo 2
Riva TNT
Geforce DDR
Radeon 9700 pro

Voodoo banshee
Voodoo 3
GeForce 4 ti series
9800pro