my list:
1. bonewall
2. phase shield
3. permafrost shield
4. others
5. fire buckler
bonewall is definitely still on top, imo. its only weakness is having to set up the board with a fire storm/otyugh if you want it to stick. even though it's not as easy to sit behind a sundial anymore while you do it, there are still many ways to stall while you set it up. being resistant to steal/explosion is a huge plus as well.
phase shield is great because it can save you from the brink of death whenever you draw it. it's second to bonewall because it only gives you a few extra turns, and you're usually using those to dig for bonewall... also, it's lack of synergy with antimatter (which i'm currently running three of) as well as quintessence (again, running three) occupying most or all of the aether slots for current rainbow decks makes it a little less appealing.
permafrost shield is what i'm currently using in place of phase shield when farming false gods (thanks puppy). it at least slows down most gods due to it's ability to freeze creatures, and virtually stops others i.e. scorpio, ferox, morte, incarnate, fire queen. it doesn't stop arsenic vs morte and scorpio, but on the bright side scorpio at least likes to play trident over the top of arsenic which has saved me a couple times.
@zhen_rogue, the freeze probability is actually 30%
EDIT: it also has a 0% chance of freezing a creature that does not deal you damage. i.e. a creature with 2 or less attack. this might be what led you to believe it was closer to 10%.
i put fire buckler at the bottom because it's not a shield. there are plenty of ways to remove creatures from the board, but only one place on the board to put a shield. you'll have a good time against dg, but the other gods have very few problems with this card. growth grows faster than fire buckler can deal damage and most other creatures will have likely done what they needed to do before they are finally killed. if you pack one these there will probably be some times where it will be the star, but a vast majority of the time it'll just be a wasted draw.