What can I say about this card that hasn't already been said? It's an important part of Ad Nauseam decks and it's just pretty great all around. It's also great against storm decks since they've usually only got one shot in them anyway. The only issue I have is that it doesn't completely stop life loss, so if you have no way to get to 1 life before the end of the turn, you're out of luck. Still, it's a great card.
Pros: Stops you from losing the game
Cons: Doesn't stop life loss
This is the runt of the litter. +5/+5 and shroud until end of turn is great, but for four, I wish "trample" was also on this card. At common, +5/+5 tends to cost at least 6 for instant-speed (see: Explosive Growth). At rare, similar cards give trample and other such niceties (see: Titanic Ultimatum). Again, I'd like this to have trample instead of shroud. Still, it's an okay combat trick that can't really be countered.
Pros: +5/+5 and shroud at instant-speed
Cons: No evasion
I've talked about this card here. I don't think I need to elaborate on it any more. It's amazing.
Pros: Makes a field useless
Cons: Doesn't affect any tokens on creatures
Stifle's big brother. For double the cost, it really does double the work. Some permanents (like Memnarch) can recover easily from having their first activation countered, but they are stymied if they can't activate for an entire turn. For the price that it's act, you can't really get much better.
Pros: Stops and locks activated/triggered abilities
Cons: Costs 2
Word of Seizing
This is a card that I don't see enough of. Yes, it costs two more than Mark of Mutiny and one more than Ray of Command for what people think is basically the same thing. But, it's not the same thing. Not even close. Say your opponent has spent a while getting his Domri Rade up to 7 loyalty. What would you rather in your hand: this or Mark of Mutiny? Say your opponent just dropped an Akroma's Memorial and you survived. What would you rather: Ray of Command or this? I'm not saying it's amazing (it does cost 5 after all), but it's good enough that it deserves more play than what it gets.
Pros: Steals a permanent for a turn
Cons: Costs 5