My first GPU came in my first computer which was a Compaq running windows ME (terrible, I know). Equipped with a 700Mhz AMD Duron. It was an 8 MB nVIDIA Vanta LT AGP card... i know right? can't even call it a GeForce.. This pc always pissed me off because it seemed like none of the games i had that i wanted to play would even run at all.. (some old star wars game, flight sim, etc)
My next PC my dad helped me build as a project in '04 ish. This thing was fairly beastly for the day. 1.5gb DDR 400, 3.0ghz northwood P4 with hyperthreading.. The gpu was a GeForce4 MX440. 128MB if I recall.
My dad, had to confiscate that pc for work, so he bought me and my brother an emachines in 2005. It only had 512MB of ram, but the athlon 64 cpu it had was better than the old P4, so I was ok with it. (despite running an entire GHz slower and having half as many threads at its disposal). That pc had intergrated radeon xpress 200 graphics which ran my games just fine at the time (flight sims, battlefront, etc). However, Microsoft Flight Simulator 10 ran horribly, so I decided to upgrade it. Mowed lawns until I could afford to max out the ram: 2gb of DDR400, and acquire a decent gpu. I read that FS10 greatly favored nvidia especially for weather, so I bought a 256mb Geforce 8500 GT.
Why was I using a single core rig in 2007? because i was a poor teenager, hence the lawn-mowing.
Unfortunately, the game still ran horribly because it is an extremely CPU dependent game. However, I was broke again until I got a "real" job. so in 2010, after saving up enough money, I built a new PC from scratch. 3.0ghz quad athlon, 4gb ddr2 800, and a BFG GTX 260, core 216, 55nm revision. My first true gamer's card, I loved that thing. I threw everything i could find to play at it. Handled FS10, (thanks to the quad), CoD, Crysis 1 and 2, Metro 2033, Battlefield 3, (though most not at max settings).
Ever since I built that PC, i've been continuously upgrading it, 1 component (or 2) at a time til the point that now, it literally shares nothing in common with the PC i built in 2010, however, its soul lives on. I finally upgraded the GPU last november when I got back from training and had tons of cash to blow, so i bought a brand new radeon hd 7870. Note, this was my first radeon card, but i've been pretty impressed. While the 260 could RUN anything I could throw at it, I've finally achieved a setup where I can MAX nearly anything i throw at it (other than metro of course).
Misc. GPUs: I've built quite a few PC's for other people since I built my first one for myself. Thrown in a variety of GPU's, such as these (based on budget and gaming/work needs)
xfx hd5450 for my dad
zotac 'ion' gpu for a friend
GTS 250 for another friend
hd5770 for another friend
hd4890 for my step brother (always loved the way they looked)
hd6850 for my brother
and, of course, an hd3870 x2 i got off ebay for chump change to see how crossfire works..