Warcraft III. Voodoo2 wasn't cutting it, upgraded to a GeForce4 MX420.

.... which still wasn't really cutting it, so I spent every penny to my name and upgraded to a Radeon 9700 Pro like 6 months later.

Man, I loved that card. Used it for years. To this day I think it was the card I held onto the longest.

Probably Dungeons of Daggorath for the TRS-80 Color Computer.

Edit- It was a Tandy Color Computer 2 circa 1986ish, went from 16K to 64K ram.

World of Warcraft. I was on Windows XP with 512mb of RAM and who knows what graphics card but I was lagging so bad when WotLK came out.

With all the people standing at the entrance to Naxx I had to basically aim myself for the portal and lag my way in without being able to see where my character was walking due to the lag.

Half-Life 2. I remember being completely blown away by early source engine, even on low graphics to keep the frame rate above the 20s. I watched the weird little graphics benchmark animation probably a hundred times to dial in the settings. If you told me that in the future I'd be capping the framerate on highest settings to keep it from hitting the default limit of 300 I'da called you a liar.

Full Throttle.

Had a 386 and the game required a 486 so I bought a Cyrix 386 to 486 replacement. Worked decently well.

Doom - we upgraded to 16MB of RAM so we could play it through Windows 95.

Win95 wanted 4MB and Doom wanted all 8 that we had, so we had to exit, reboot, and go to DOS then run it manually.