On my DOS machine I have this little space-saver PS/2 keyboard which ticks all the right boxes but has some serious deficiencies:

I love the idea of this thing - getting a full set of arrow keys *and* a proper numeric pad in something 2/3 the length of the Sun is awesome, but the actual layout is really poorly thought out. I constantly overshoot the backspace and get 'home' instead (infuriating) and delete/insert (between the arrow keys and ctrl) are way easy to hit if I misplace my right hand. Also I wish it didn't have the windows and menu keys either, they just take up space. Oh well, it was $2 on Tradme, and it's black.
For my "modern" (USB-capable) systems, I scored one of these recently - a Sun type-6:

Not the springiest in the world but I like it. Thankfully I have the "PC" layout which has control/caps lock and backspace/backslash in their usual locations. Supported natively by both KDE/X11 and OSX, but the Sun special key block on the left doesn't do much. Can be remapped in software though.
I seem to be in the minority in that I don't particularly like Model Ms, they're just too clunky for me. I can use one, I just type faster and more fluidly on a membrane keyboard. Usually. I think the best 8-bit keyboard I ever tried was on an MSX but I don't remember which model.