For those who don't play Hearthstone, Magma Rager is seen by many as one of the worst cards in Hearthstone.
While some "bad" cards can sometimes find home on niche decks (like Naturalize on Mill Druid), Magma Rager is on that sweet spot it's bad, but don't provide any special effect noteworth.
And for those curious, it's badness come from the fact it only has one HP. It's very hard for it to survive until the next turn and it's trivial to remove.
For the sake of comparision you could just put a Injured Blademaster (4/3) or a Jungle Panther (4/2 Stealth) for the same cost.
I still think eventually we will get a legendary who generates Magma Ragers just so it will see some play.