The Social Vampire
1. Effectively drains an enemies health and returns half of it to you by leeching via a pair of fangs shot from the weapon.
2. If health is low and no one is around to give you a boost, you might as well DIY.
3. To gain health, you must have TWO people leeched at once, otherwise no health is gained and the pair of fangs only deal slight damage, so while you can get all your health back from two people and kill them at the same time, you are open to twice the fire, plus it takes three seconds to fulfill the whole draining process (maybe holstering a certain sidearm reduces this time).
4. The game would, of course, have to use the master race of health systems (non-regenerating and denoted my numerals), and be largely team-based so that you could actually FIND a pair of enemies to latch onto.