Vial Smasher the Fierce is a Commander with Partner that could see play in Legacy.
Whenever you cast your first spell each turn, including on your opponent's turns, Vial Smasher deals damage equal to that spell's converted mana cost to a random opponent. Because this damage is random, she is probably not going to be very popular creature in a multiplayer Commander game. Vial Smasher is really more of a nuisance than anything else, but you can get a ton of value out of this ability.
In a one-on-one Duel Commander game, however, Vial Smasher is extremely powerful. Since the ability is always going to hit your opponent, it can become a very short game. Duel Commander starts with a much lower life total. It used to be 30, but this amount was lowered to 20 in September 2016. This could be one of the best commanders in that format.
Keeping this in mind, could Vial Smasher even be Legacy and/or Vintage playable? Keep in mind, casting a Force of Will, even for its alternate casting cost of exiling a blue card from your hand and paying 1 life still has a converted mana cost of 5. As Vial Smasher is only 3 to cast, it's possible she could be a way to finish off a game in what's usually quite a fast format.
It also seems possible that Legacy Burn may want a copy or two of Vial Smasher. Even an extra 1 or 2 damage goes a long way in those decks. In Vintage, there are some big spells that get cast, so Vial Smasher can win the game if she's on the board when they are. This seems like a card that could show up occasionally in these formats.
As a Partner, Vial Smasher not only gives access to Red and Black mana, but also gives a way to deal a lot of damage out of nowhere. While it's rare that she'll just kill a player out of nowhere, spreading the damage around just for you casting spells is an extremely efficient way to close a game out quickly. I think this gal is going to see a lot of play as a lone Commander, a Co-Commander, and as one of the 99. And if Vial Smasher is as good as she looks, she may even pop into competitive Legacy or Vintage!