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While I know refering to the stack is generally a no-no. I had this idea, so here it is...

Rush of Creation 
Sorcery
While ~ is on the stack, creatures you control may tap as though they had haste.
Reveal a card from your hand, then reveal the top card of your library. If those two cards share a card type, you may cast the card revealed from your library without paying its mana cost and as though it had flash.

Ward of Life
Instant
While ~ is on the stack, any life you would lose is reduced to 0.
Gain 5 life.

Slaughterhorn Goblin
Creature - Goblin
While ~ is on the stack, creatures you control have ": This creature deals 1 damage to target creature."
When ~ enters the battlefield, sacrifice it unless a two or more creatures an opponent controls died this turn. If you sacrifice ~ this way, it deals 4 damage to you.
4/2

Azerot, Lord of Death 
Legendary Creature - Demon
While ~ is on the stack, spells your opponents cast cost an additional 2 life to cast.
Flying, Trample
Whenever you cast a spell, you may sacrifice a creature. If you do not counter that spell.
6/6

So whats the word? 

Generally I was thinking small "extras." Though using it as a drawback is a neat idea....

Flareblast
Instant
While ~ is on the stack, instants your opponents cost less.
~ deals 5 damage to target opponent and each planeswalker that player controls.

Though I was thinking more... synergistic (?) effects:

Rush of Inspiration
Sorcery
While ~ is on the stack, spells you cast have cascade.
Draw cards equal to the number of spells you've cast this turn, then pick x cards in your hand and put the rest on the bottom of your library in any order.