I had some old ones laying around, so I put them on a sheet. I had one with lots of kind of monotone ramps and it didn't cover much of the color space. Then I had a few others that I've made from my histogram stuff. Today I made a 4bit per channel (4^3=64) and it left out too many grays. Finally I just made 3 of my palettes into a single palette using PS, then I noodled on the ramps. It covers the color spectrum pretty well. I put some special colors in there like duck egg blue, skin colors, etc. Sky gradient got a lot of colors, maybe too many. I generally avoid magenta hues in sky colors, and teal-green. I haven't paid any attention to brightness based cross ramping, but I threw out some colors (seen under the final top right chunk) to get a longer plain grey ramp in.
Follow the arrows. Top right is final. Top left is some old thing I made ages ago, but it's too ramp oriented and kinda dull, and it doesn't cross ramp much.
I save the 4*16 chunk as raw and open as binary in my programs. This is a HSL cylinder I believe. I can slide the discs up and down to crop out colors. It rotates too. The ramps don't really show though (with so few colors and equally spaced neighbours). I'm not sure if the palette should spend a lot of indexes on ramps though... It's a balance between coverage versus gradients. I tried a palette with more focus on ramps and it fails to explore a lot of the color space. I'm very partial to flat looking gfx with mostly light and shadow. I don't like gradient / 'chrome' crazy games like we saw back in the Amiga days.
For reference, the 4 step generated palette with maximum coverage.
Here I tried unwrapping the colors onto a 2D plane, which is impossible of course. Basically they just try to keep their ideal RGB Pythagoras distance. It looks a bit like people pushing around in a crowd before they find their places. (The dots aren't round because the iMac is immensely slow at screencapping, it takes several frames so there's frame tearing of sorts with the dots jittering about. I shake them into place.)
Here's 256 colors. They're kind of sorted I guess. One solution could do some kind of regional bias so colors will prefer certain places based on one of their dimensions.