Feeling a little like a mortal kombat designer after that subject line.
Magic commentary follows, so I'm snipping it.
This set rocks much harder than Kamigawa. Yeah, I'm glad the Kitsune came out in Kamigawa, but there really wasn't anything in that block that caught my attention. Ravnica is the complete opposite, and there's so many cards that are begging to be broken it's not even funny.
You thought the Martian Death Crab was bad? These, my friends, have potential to take the MDC mk. 7 to all new levels of DEATH! Oh, and as a side benefit, they're potentially really evil in other decks, too.
Tidewater Minion
This sucker costs 3UU, and is a 4/4 with defender. You can pay 4 mana so that it'll be able to attack. It also has "T: Untap target permanent".
I know what some blue mages are thinking: "OMG! 4/4 beatstick for blue that's not insanely expensive!" These blue mages are idiots. The true power of this guy is in his special ability. For example, let's say you enchant this sucker with Freed from the Real (which lets you pay U to untap it). All you need is a way to generate at least 1 blue mana reliably. For example:
Tolarian Academy + Freed from the Real + Tidewater Minion + 2 artifacts. The Academy is tapping for UU. You're paying 1 to untap the minion. What can you do with infinite mana?
There's so many way to get infinite mana out of the minion it's not even funny. I can think of at least 2 more off the top of my head. But there's also the general utility you can have out of being able to untap any permanent you control...if you have, say, an Icy Manipulator, Avatar of Woe, and Temporal Adept out and they're all tapped, you opponent still can't plan around the fact that none of them are available to use. The minion basically seves as an extra copy of any card on your side that you tap to activate.
Stone-seeder Hierophant
This sucker's similar to the Tidewater Minion, but it's a little harder to pull infinite mana out of...it can be done if you use old cards (hint: Fastbond) and gating lands (think things like Boros Garrison). It works well with cards that let you play multiplel ands per turn as well...but the only way to go truly infinite with this thing is to be able to play infinite lands.
Terrarion
Remember all those cards from fifth dawn that pulled artifacts with casting cost 1 or less back from your graveyard, or let you tutor for them? Well, this thing only costs 1 mana. I'm still working on specific combos using this thing...but I will find a way to break it, oh yes.
Coalhauler Swine
So, alright, the way this guy works is as follows: Whenever it takes damage, it deals that much damage to each player. Let's say you put Pariah's Shield on it. Now any damage that goes to you is redirected to the Swine, which will then go off and damage each player. The damage'll be redirected to the swine and so on until the swine itself dies.
i.e. You take 1 damage. That 1 is redirected to the shield equipped swine. The swine then does 1 damage to each player, yourself included. The 1 damage is then sent to the swine. At the end of it all, every player but you has taken 5 damage, and you've only taken 1 (just trust me on this one...the guy who writes Saturday School on the wizard's site went over how this works out).
So what happens if the swine is indestructible? That's right! As soon as you or the swine take 1 damage, you win the game, provided no one disenchants the shield or terrors the pig out of existence.