Dryad Arbor

A Forest that is also a 1/1, and that tiny contradiction is the entire reason it exists. Because it carries the Forest subtype, any fetchland that searches for a Forest can pull it onto the battlefield instead of a basic, and Green Sun's Zenith for zero finds it at the bottom of its tutor list, turning a one-mana tutor into a creature that drops a green source straight into play. That single trick is why it spent years quietly enabling some of green's most efficient one-drop engines: a body that arrives without being a spell, untaps for ramp on a later turn, and feeds anything that wants creatures on the table or counts them in the yard. The summoning sickness clause is the tax that keeps it honest. Brought in under its own power, it cannot tap for mana or attack the turn it enters, so the card refuses to be a free accelerant; it asks you to plan a turn ahead, or to cheat it in through an effect that cares about creatures rather than mana. It also inherits every downside of being a creature: it dies to removal, gets swept by board wipes, and can be chump-blocked into a trade you did not want, all on a permanent you were treating as a land. That fragility is the cost of the flexibility, and the reason this remains one of the strangest fault lines in the rules: a permanent that is fully a land and fully a creature, with no compromise between the two.