I wanted to take a crack at making an articulated action figure for myself, and this is the current product. The figure can be assembled without any glue or fasteners, and has 14 points of articulation. The hands are roughly sized (somewhat arbitrarily) to hold takeout chopsticks. I will be continuing to develop it to improve the poseability and style, and to add features/accessories, so if you don't like it right now, check back later.
If you want to make your own parts, the balls are 10mm in diameter, and the pegs are 3.8mm in diameter to fit 4mm holes.
Almost all the parts can be printed with 2 shells and 0% infill. The hips and torso should be printed with coarse infill, and the pegs should be printed with 4 shells and 0% infill to make them solid. No rafts or supports are necessary. Assembly is pretty self-explanatory. If you are having trouble getting things to fit, needle-nose pliers will help you get a grip on parts, c-clamps or a vise will help push parts into place, and needle files may be needed to open up holes. Cyanoacrylate glue can be used to hold the pegs in place, especially at the wrists, but only put it on one half of the peg or you will lose some of the articulation.
4x biceps, sockets
2x forearms, thighs, calves, foot
1x head, hips, torso, lefthand, righthand