I've got an awesome one. Now, this isn't because I'm a selfish engineer looking out for myself. It's really for the benefit of the team. Not even sure if it's great for a last skill but it'd be cool to have. I'd call it Vampire or Vampiric Leech. It allows you to drain/rob your teammates of some health collectively to give you a boost of health to stay alive...of course for the purpose of keeping the whole team alive and preventing a wipe. Or maybe not...muwahahaha! *evil laugh*