Cast Out
 
It's funny how just a couple of words change a card so much. I guess when those words are Magic keywords, it makes sense. Oblivion Ring is one of the most powerful cards in Magic's modern era, so giving it a whole extra level of flexibility makes for a very dangerous card. Cast Out isn't a complete or automatic upgrade, though, because of its higher converted mana cost - the game state on turn four can be quite different than turn three, specifically in a way that you often need to get more than one thing off the table. Even at instant speed, exiling just one won't always help you so much at that stage of the game.
 
Constructed: 4/5
Casual: 4/5
Limited: 4/5
Multiplayer: 4/5
EDH/Commander: 4/5