Vampire Hexmage

The sacrifice ability looks like incidental counter-removal: pop your Vampire to wipe planeswalker loyalty, clear a stray pile of -1/-1 counters, reset a charge counter or two. That reading misses the most important word on the card, which is "all." Pair it with Dark Depths, a land that arrives with ten ice counters and demands you remove them one painful payment at a time before it ever makes a token, and a two-mana creature with first strike turns ten counters into zero at instant speed. Dark Depths reads its own state-trigger the instant the last counter leaves, so sacrificing the Hexmage in response to a removal spell or simply on an empty board hands you a 20/20 indestructible flying Avatar far ahead of schedule. That interaction defined a real competitive combo for years and pushed the front half of the pair onto restricted lists in older formats. What makes the design genuinely clever is that the body is honest on its own: a 2/1 first striker that trades up in early combat and threatens to brick a planeswalker the moment one shows up. The combo never asked you to run a dead card waiting for its partner. The counter-removal clause was written broad enough to be useful in a dozen mundane situations and broken in exactly one, and that asymmetry, a reasonable creature concealing a token-generating engine in a single line of text, is why it endures.