For me it's hard to choose because I had several models mentioned above and each one of them marked an era of my life.
I started with an IBM PC 286 where I learned to use DOS and where I started to play some games that I still enjoy today like PreHistorik/2, Keen, Lemmings, Pacman, Bumpy and much more...
Later I had my first Windows 95 computer which was a Pentium 166Mhz MMX with 16MB RAM where I played among other games, Age of Empires, Theme Hospital, KKND, Seven Kingdoms (yes I am a strategy game lover), etc.
Later I had an ADM K6-3 400Mhz with 4MB cache L2 which was a beast at the time! It was there that I also had my first 3D VooDoo 2 Video card that allowed me to start playing heavier games like Carmageddon.
So my choice goes to Socket 7 (later Pentiums usually with MMX, add K6-2s and K6-3s, add Cyrix).
Each one of them allowed me to live each era and they were just fantastic.