Currently we are running out of truly broken cards from the Premier set, so I might as well talk about the elephant in the room, Rarity Truly Outrageous. This card is ridiculously broken, you could even say redonkulous (I won't, but you could)
Because of the lack of reactive control in the premier set there is almost nothing that the opponent can do to stop this card from steam rolling. The way this card is broken is obvious, so I'm going to do something a bit different today and talk about how you might be able to counter it.
How can I possibly beat this grinning demon?
(There's a TLDR summary at the end if you don't want to read all of my rambling.)
Option 1: Control
For this option you want to run control cards. Anything that can force discards, dismiss friends, or frighten friends will help. If they aren't running a white Mane Character, try and prevent them from getting to two white threshold as long as possible. If Rarity is already out, send her to the discard pile ASAP with Downright Dangerous. This option is far from fail-proof, so just try and win as fast as you can. Mayor Mare and Stand Still are also a good way to set up a dismissal, as most dismissal cards require the Friend to be at a problem and Rarity likes to just sit at home. Inspired friends can help here as well, by preventing your opponent from ever drawing Outrageous Rarity. Speaking of prevention...
Option 2: Prevention
Besides just running Inspired cards to prevent your opponent from drawing Rarity, run anything and everything that makes it hard from your opponent to confront the problem. Stack your problem deck with difficult problems, run Troublemakers (the more powerful the better), and run Screwy Barking Mad, Snips and Snails, and Old Salt. Troublemakers and the friends mentioned will all prevent your opponent from easily confronting problems. Bright Bulb Seasoned Strategist can also help a little bit here, since he can force an opponent to pay to move Rarity even when she's first played.
This card is frequently overlooked, but a perfect counter to Truly Outrageous so I'm giving it it's own section. It can serve dual purpose locking Rarity at Home or at a problem, since she can't move to trigger her ability. It's also a really good card that is under used, so just put it in your deck already.
Option 4: Wait for Canterlot Nights
This might not be to everyone's tastes, but it really is a good option. Canterlot Nights will almost certainly contain cards that counter the most broken cards from Premier. In fact, one has already been spoiled: Chief Thunderhooves. The chief will only do anything if it's the first time your opponent is playing Rarity, but frightening her right out of the starting gate is a good option. There will also probably be reactionary dismissal, frightening, and exhaustion cards of all stripes, so the ability to play a reasonable control deck will go up significantly.
TLDR, So how do I beat the dang card?
Run a Pink/White control deck with play-sets of Downright Dangerous, Tangled Coiffure, Barking Mad and Snips & Snails as well as several Inspired friends. You'll have a good chance of stopping Outrageous Rarity in her tracks.
Right now Rarity Truly Outrageous is riding high, running a minimum of 50$ on haluz.org. This price won't be sustainable, especially after Canterlot Nights comes out and there are more options to deal with it. It's still a damn good card, so it won't lose all of it's value, but it's probably not a good investment right now. I have a feeling the bubble is about to pop.