So, I found a lvl 46 Torgue shotgun with insane elemental damage, which suited my elemental Amara build just fine.
The protuberance fires one projectile in an arc and explodes into three projectiles upon impact, which arc away a very short distance and leave an elemental cloud behind.
Even in lvl 50 TVHM, the damage from that gun is enough for almost every enemy.
Still, one always wants the better version and Marcus had a level 50 Protuberance on sale. It looked like this:
The level 50 version was much worse than the level 46 one, which makes me wonder: Did I grab a bugged gun? Or do the prefixes make all the difference?