Heart Inject

[BaneOfGiygas]

While cool in concept, this would basically mean that someone has the ability to infinitely retain a particular chemical in their bloodstream forever. Mix up some stimulants and put them into you with this thing and suddenly you're invincible. Put poisons in it and stab someone with it and suddenly they're basically doomed to certain death unless they get a heart transplant.

Unless someone can come up with an idea to make this work that's actually balanced, by vote goes for no on this one.