@digikitty_x86 Cross-posting my answer from twitter. While I would love to say my Altair is mine, honestly my favourite would have to be my Turbo XT system. Something about a slow #DOS machine.

10MHz NEC v20, 640k of RAM + 2MB EMS, dual #CGA/#MDA video, a #SnarkBarker sound card, and ethernet. The XT is one of the oldest platforms with a native TCP stack #mTCP which makes it quite usable even if single tasking.