Venser, Shaper Savant

The genius is in the words "spell or permanent." Counterspells answer spells; bounce spells answer permanents; this single trigger straddles both, and the flash on the body means it can ambush either window at the moment you want it. Hold it up against an opposing finisher on the stack and it functions as a counter that leaves a 2/2 behind (the spell returns to hand, not the graveyard, so it is a tempo answer rather than a permanent one). Or flash it in past a board state and reset a creature, a planeswalker, a land you want to replay, or your own permanent for value. The trigger does not say "target spell on the stack" or "target permanent an opponent controls"; the wide-open targeting is the whole engine, and it can be pointed at your own things to dodge removal or rebuy an enters-the-battlefield effect. None of that flexibility comes free: it answers nothing permanently, the body dies to anything, and a bounced spell can simply be recast. But as a Wizard you can flash in at instant speed to interact with the part of the game most blue interaction cannot touch (a permanent already resolved) using the same card that handles the part it usually does (a spell mid-cast). That convertibility, one card covering two phases of the game depending on when you blink it onto the table, is why it has outlived most of its contemporaries.