The ultimate is definitely this one, which just had a V2 kickstarter
Assuming you want the absolute minimum size case that also fits a full size GPU, that is. It’s less critical than it used to be because Thunderbolt 3 lets you use external GPUs, at some extra expense and with 10-20% perf loss, on any small PC with a Thunderbolt 3 port.
(well, minimum that isn’t insane and requires crazy hard build)
