Farseek

Search your library for a Plains, Island, Swamp, or Mountain card, not a basic land. That single word omitted from the oracle text is the engine. Because the spell asks only for a land carrying one of those four subtypes, any nonbasic wearing one answers: a shockland, a typed dual, a Triome. A basic-fetcher like Rampant Growth can pull only a single-color land out of the deck; this one retrieves the actual color-fixing the manabase wants, and its ceiling has climbed every time Wizards prints a more sophisticated typed nonbasic. The deliberate exclusion of Forest does the rest. A green deck already has its own color in abundance, so refusing to fetch Forest is the spell's reason to exist: the piece that makes it connective tissue for three-color green ramp rather than a redundant accelerant. The tapped clause sets the tempo cost. Cast on turn two, the fetched land enters tapped, so the acceleration arrives the following turn rather than on the spot. Strip away the typed nonbasics and you are left with a fragile, color-light ramp spell. Build a manabase whose duals all answer to the search, and you have one of green's most durable fixing pieces: a card whose value has been written as much by the lands printed in the years after it as by its own two lines of text.