NECK BRACE:
Probably saved myself from serious injury wearing mine on the weekend, going headfirst into a boulder isn't to fun, I always were it when I ride DH
BACK/CHEST ARMOUR:
I only wear my pressure suit for harder/rockier courses where there is more chance of stacking/it would hurt more. It has saved me while a few times from getting beat up and I was able to keep riding. For easier/flowier courses I choose not to wear it because it is bulky and can be annoying to wear.
KNEE/LEG GUARDS:
Judging from the hundreds of scratches in the they're saved my shins heaps of time from shin-bashes and also my knees from quite a few stacks, I also wear them when riding DH because when I haven't I have screwed my knees up quite a bit when I've crashed
ELBOW/ARM GUARDS:
See Back/Chest Armour, pressure suit, built in
GLOVES:
Only reason I wear gloves in for grip, not protection though they do save your hands from grazes, not much else
GOGGLES:
Keep me to not crash, keep dirt/dush/water/mud out of my eyes, always ride with them whenever I use my fullface.