The most expensive cards are Skullclamp, Attrition, and Lightning Greaves
Maybe now you will
Off the top of my head, in Standard and Modern, it prevents some or all of the use of the following cards: Every flashback card (in particular) Ancient Grudge Desperate Ravings Dread Return Dream Twist Faithless Looting Forbidden Alchemy Mystical Teachings Past in Flames Think Twice Unburial Rites Snapcaster Mage Narcomoeba Reanimate Exhume Every undying creature Every persist creature Gravecrawler Ichorid Ashen Ghoul Proclamation of Rebirth Polymorph Probably quite a few others 1) Drogskol Captain Hexproof is a very non-interactive creature mechanic, making it one of the more powerful mechanics to have been printed in recent years
Of course, DraftSim has had its Phyrexia draft simulator up for nearly a week now, so you might've had a chance to try out the set already
Think Isochron Scepter combos, Voltaic Key combos, Sword of the Meek + Thopter Foundry
In this case, flipping doesn't mean throwing the card in circles from one foot about the playing area like with Chaos Orb
