Engineers can make jumper cables to shock downed allies back to life. After you try, you won't be able to use them for about half an hour... BUT another engineer can. Jumper cables don't bind to you, so you can pass them around as much as you want. I was in a raid and a couple of the hunter engineers were the only ones to survive a total massacre. My cables failed and we all thought we were done for. Then I passed them to the other engineer and he was shocked to see it worked. We got the priest back up and the raid kept going. If one engineer has better cables than the other in a group, be sure to give him a try with the better cables.