Heró
OG
Im probably not the first to find this, but if you talk to an elder and do their quest (rewards no xp) they mail you a lucky red envelope. you've got a chance of lucky rockets in their, firing these gives you a 250 buff 
the most useful thing about this is that its an AOE buff, and with an engineer crafted firework cluster launcher you can ask everyone to gather around and your whole team will pick up the buff, thought it might be useful, especially at 19
the most useful thing about this is that its an AOE buff, and with an engineer crafted firework cluster launcher you can ask everyone to gather around and your whole team will pick up the buff, thought it might be useful, especially at 19