a hard one. my first card was a S3 ViRGE with 2 MB EDO RAM, pretty shitty card that was later replaced by a Rendition Verité V2200 8MB RAM. Firsty i was really happy, because the new V2200 allowed useable 3d acceleration, so i could play stuff like Quake 2 and Tomb Raider 3, however later I realised that the card completely sucked at 2D, so a lot of favorite old DOS games became unplayable on it.
next, i had a GeForce FX5200. I know this was a shitty card even at the time of release, however considering the fact that i used a PCI version on a 1Ghz Celeron, i think it had more than enough power for that system. Actually this is the video card that I liked the most, I used it mosty to hook up my computer to the tv and watch movies - pretty nice memories actually.
Then my current card: Radeon X1950 Pro - the most powerful yet, however i had quite struggles with the drivers. I am thinking about replacing it, however Nvidia has currently nothing to offer, and im not sure whether i want another ATi card...