I'd love to say that it was my 2600k @ 4.8ghz build with 16gb ram in 2011. but that's a best LONG LIVED build.
What was the most significant bump was going from a P166 with 80mb EDO memory, S3 virge 2d, Voodoo 2 8mb 3d box I used from 1996 to 2001., 1.2gb HDD with 15" 1024x768 CRT
THEN:
My dad got a new job and knew how much I loved computing, he said go build your perfect PC and That your Christmas!
I went to m-wave and built out an AMD t-bird 1.4ghz (fastest cpu you could buy). 512mb DDR (or was it SDRAM?), two WD 100GB HDD's in raid 0 (bad idea 6 months later lol), and I believe an ATI 8500 (first tesselation in RTCW). And the most expensive part was the $850 Sony 21" CRT trinitron. I used that sucker until 2009.
I also got upgraded from 48.8k dialup to 1Mbit/s cable internet.
Talk about a huge jump in computing. Everything was amazing exponential. My dad made my YEARS.