Redirection seems like a staple to me. Even if it was just another misdirection it would make my stack but I think the ability to change all the targets makes it better than anything but Misdirection itself in that department. It won't always act differently. Deflecting violent Ultimatum, Relic Crush, Double Negative or even other misdirection spells like Shunt will not happen often or consistently, but when it does it should be really powerful.
Wild Evocation seems nice because it forces them to play the spell, which probably means the next few mass removals will nuke down everything. OTOH, if players don't have enough mass removals, the game will be very hard for everyone to keep under control. This is what I want my game-altering effects to be like. Is there a way to cast a spell in response to the trigger so that if they reveal a counter they will have to counter your spell?
I will play Leviathan, but I'm not sure it's so strong. It would be better if it was like the Archon - people cannot attack you but are welcomed to attack your opponents. The Archon is not Glarecaster level, because it doesn't have the combo kill, but is good enough anyway, I believe.
Copy target instant or sorcery spell. You may choose new targets for the copy.
A reprint of Fork. I don't have the original (only Twincast and Reiterate) so I will play it if I get one.
Mass Polymorph 5U
Exile all creatures you control, then reveal cards from the top of your library until you reveal that many creature cards. Put all creature cards revealed this way onto the battlefield and shuffle the rest into your library.
Unlike Warp World, I think this card does have some merit. It is very situational though, so probably it still doesn't make the cut.