To auto-revive:
when dead but waiting for someone to revive you press the keys "x" and "C" and you will be able to move shot etc. again while unable to do task that require SPACE BAR.
MK20 20MM bug:
take the too bags of the disassembled mk20 and try to mount it in the highest par of the towers or in the rocks looking at zaros that are nearby ( in the rocks it doesnt happen in every spot) when you click mount the mk20 will be mounted in the ground instead of where you left the bag.