For me. Shoulder and knee is the most important joint coz if u get it broken or cuted u fall like a sh-t or cant run..

they're all worthless without the help of eachother. if we're going for most useful combination of joints, i'd say wrist, shoulder and pec.

Well, I suppose people who plays different mods have a different opinion about how joint works.

Yeah but at least most joins are pretty predictable when frac'd they just act like relax'd, knee joints hyper extend, I mean you really can't use them for anything.

Neck, because you don't think you need it so you don't take any actions to prevent your head from dq'ing if the rest of your body works.
The thing about dq'ing your knee is that you can still kinda use it, if you make the knee bend forward and keep pressure on it, you can still use your leg to stand on.

neck
'nuff said

to me, they are the whole of lower body, following what pusga said
AND DONT YOU FORGET ABOUT THE BUTTCHEEKS GLUTES

It's almost impossible to chose, because you use each one in a different situation. Overall though, I find my chest is always doing something so I guess I find the chest one of the most important joints.

Wrists are the most important to me. I depend on those joints a lot.

knee's and pecs are most important to me.. also a bit of the shoulder i guess, that helps so much depending on the mod i guess.