One of the most infamously powerful spells in all of Magic is Force of Will, which demonstrated to R&D that free spells in general and especially free counterspells are ripe for abuse. But Force of Will wasn't a one-off card; it was a member of a cycle of "pitch cards" with alternate costs of exiling a card of the appropriate color from your hand. From the original Alliances version of the cycle have sprung many rehashes and homages, but none in recent years.
When cardboard-crack asked Mark Rosewater, "Why aren't there more pitch cards? Is it a design issue or development issue?" he answered:
A little of both. Cards that do not cost mana are developmentally dangerous plus there are only so many effects you want to let be free and we’ve done a number of them. I’m sure we will do pitch cards again one day although I don’t know if they will be in a Standard-legal set or a supplemental product.
With as swingy as pitch cards are, they're nevertheless popular. Formats exist that can tolerate that kind of power; Commander products, for example, seem ripe for a full-cycle reprint of one of the horizontal cycles of pitch cards or else an entirely new one, perhaps with a multicolor variant.