One of each per faction or one of each total? Like you can have one for your Autobot unlocks and another one for your Decepticon unlocks. For example, if a Prime core is used on an Autobot, does that mean it's not available for the Decepticons to use because there was only one? The Death Pulse core is the one I absolutely refuse to use, I tested it and it didn't work well. Medics are usually my first priority for Rejuvenate cores, but First Aid/Reflector would be the one I'd start with, since they've got those little helpers. I assume the helpers don't get the Rejuvenation benefit, that it is for the primary user alone. I also gave one to Springer, since he's sortof a healer. When I first started playing around with cores, I got so confused trying to work out which class benefited most from which immunity core, because they only worked vs specific weapons. In the end, I just gave up and chose to focus on cores that provided a constant benefit not dependent on external factors. If feedback is to be offered on game mechanics, I would request that at least a few responses be made, so as to confirm it's not an individual opinion. Please do not assume that just because one response is written that another response won't be of merit.