Looked at several vices, some nice designs around, but I wanted (A) 100% printable, (B) Simple, and (C) Strong enough to actually use. Didn't find anything that really met my needs, so I made my own.

6 parts, you'll need 4 of the pins, one of everything else. Assembly is pretty straight forward.

Printing: I tried for minimal support required.
Frame: Print flat, no support.
Face: Print frame interface up, I needed trees to get a good round hole.
Foot: Same as the face.
Screw: Print standing, only support I needed was a bit to hold open the square hole at the top. Needs some heft, I used 5 walls and 40% infill on this bit.
Pins and Handle need nothing.

Never did come up with a good way to secure the handle... doesn't bother me to let it slide a bit.

Screw is really the only thing under stress, print it strong. Everything else I printed at 3 walls and 15% infill. I used ABS... but whatever. Took 160g of material... Not too bad.

Edit:  I decreased the thread pitch, increasing the speed of opening/closing the vise.  Was a bit too slow for me.  18tpi to 8tpi.  Helped immensely.  Just needed a new foot and screw.