Aside from Black Knight, Order of the Ebon Hand (if you are playing with Fallen Empires), and Wall of Putrid Flesh (if your opponent mis-built his deck), Swords to Plowshares can deal with every creature in the format
I think it's "fringe"
While we've got dedicated guides like this one on where to buy Pokemon TCG Chaos Rising or where to buy Pokemon Ascended Heroes, I've also set our price-matching software off on a hunt for deals
Both apply continuous advantages to the players who has them, both apply to one and only one player, and both have very narrow interaction with other cards, only ones that explicitly mention them
Sure, four damage to a dork can be good but it doesn't kill everything, it kill almost nothing that important to kill and leaves you with a body that is almost impossible to get any value from offensively
Commander decks often sacrifice a theme for a good card