Well.... there is one deck that right now where I live is considered the god of all unlimited decks. So far it is undisputedly, the best out there. Though, it uses cheap cards in order to do it, but it works none the less.
The deck is muk/banette. Uses fossil Muk, shuts down powers making things like raindancing toise/suicune ex's or toise/TAwalreign completely demolished.
Then it uses energy and super energy removal to take out any special energy cards your opponent plays, or to take out a basic or two from a pokemon that may become a threat.
Next, banette, the main attacker of the deck, comes out and just rampages dealing incredable amounts of damage, and it keeps increasing for each special energy in your opponent's discard. Sweet part.... it only costs 1 energy of any type to attack.
The whole deck is considered a big tech deck, since you can literally make the deck bend in any direction so it fits your style. Heck, you could add energy roots to make banette a 90hp tank or do the lass+Eeeeeeek combo.
Now, you may be thinking, what about slowking/sneasel beating it? This type of deck faced all the Slowking/sneasel decks in the Oregon or NorthWest Regional Championship and beat the living tar out of each and everyone of them.
The only decks that has succesfully beaten this deck, was my MAGroudon/Muk, and that was because start of the game I went first and I started with lone tyrogue and my opponent a lone cleffa. 2 heads in a row and I won first turn of the game. Then a mirror match against another muk/banette, which, if you want a real match where a single mistake makes you lose the game, then this is the match up. So basically, unless the muk/banette gets a horrible start, victory is pretty much insured.
Everybody has tryed to come up with a counter to the muk/banette over here, but there has been no succesful counter that hasn't sucked against every single match up there is.
Though, there is a very punishable thraw back to the deck. This type of deck is very picky on who uses it, even though the design seems pretty simple. Out of every player who plays unlimited in Oregon, only 3 persons, including me and the orriginal creator, Jeremy or JJBGooberman on some forums, has acctually made this deck work consistantly.
Everyone else has never gotten the synergy or strategy of the deck to work continuosly. Like, in matches where muk/banette should have never lost a prize to, it comes down to like 1 prize a piece. For example, a freind of mine using this deck played against a mewtwo ex deck. GG Mewtwo ex, or you'd think. He has such horrible luck with the deck that he barely beat it after making it come down to the last prize for both players.
So basically, if your looking for a deck to beat the rest, then muk/banette is what you'll want to run. Though, that's if you think you can handle it. If ya want a rough decklist or anything just PM me.