If we're talking strictly design, my personal favorite is a generic fat PS2, probably tied with my model 1(?) Sega Genesis (none of the things like 32x or CD, which I desperately want to get some day).
If we're talking like PC with OS, the 90s Amiga lineup because I think the Amiga Workbench 3 line and the icons they used look absolutely beautiful. Definitely would love to get my hands on a 1200, but they're expensive. So no getting into that hobby for me just yet.
About the A1200, I think there's a niche for Raspberry Pi cases that look like vintage computers. Imagine having a case that looks like an A1200, another one that looks like a Falcon, the Sony HitBit, ...