The Classics
Dispel - Useful for winning counter-wars or to counter removal spells. It's really hard to say anything else without being redundant.
Ceremonious Rejection - For Tron, or any other deck with a bunch of colorless stuff in it. Again, kind of redundant.
Relic of Progenitus - It is better than Tormod's Crypt in a vacuum, but works against the Bedlam Revelers. You can always side out the Revelers after game 1, though, so there's that.
Grafdigger's Cage - Pretty good graveyard hate that doesn't affect our own.
Spreading Seas - Good against Tron, greedy mana bases, manlands. It costs less mana than Molten or Stone Rain, however it isn't an instant or a sorcery so it won't trigger Thing in the Ice
, Young Pyromancer, or give Bedlam Reveler a discount.
Electrolyze - Very good against tokens and Lingering Souls. It can also hit mana dorks, Thalia, Guardian of Thrabens, Dark Confidants, Snapcaster Mages, etc.
Echoing Truth - A good catch-all, especially against tokens.
Slagstorm - Supposedly good for dealing with Meddling Mage since they usually name Anger of the Gods. It also makes for a decent replacement for Anger if you're on a budget.
Counterflux - Good spell in the Storm matchup, albeit a little on the slow side.
Molten Rain/Pillage - For Tron, sometimes better than Spreading Seas because they're sorceries.
Ghost Quarter/Field of Ruin - For Tron and Five-Color Humans. I'd only put them in if you have a more consistent manabase than the one listed above because being screwed on colors sucks.
The Newcomers
Amulet of Safekeeping - From M19, great against Storm, Burn, and Tokens!
Alpine Moon - Yet another decent Tron hate card.
Justice Strike - It can be a budget replacement for Lightning Helix in the main if you need it, though it doesn't make up for the loss of lifegain (maybe play 2 of it and 2 Blessed Alliance).
Mystical Dispute - A decent counterspell you could use in sideboard.
If you have any other good sideboard cards to suggest, go ahead and tell me in the comments.
