Gobland

A Mountain that swings. The design collapses two roles that have always been kept separate: the source that produces red, and the body that attacks for two. It comes down as a land (no stack, no counterspell answers it, none of the cast-time tricks a creature carries) but it is a real creature once it lands, so it enters affected by summoning sickness and cannot tap for red or attack the turn it arrives. From then on it is a genuine 2/1 that also happens to be a Mountain: it eats a removal spell exactly as a small red creature would, and it fuels a curve the way a basic would. All the tension lives in the parenthetical bookkeeping, which spells out that it plays by land rules for the stack and creature rules for the board at the same time. The one restriction that pays for all of this is that it can't block, an honest tax on a permanent that develops your board and your mana in a single drop but cannot also be your wall. The silliness is the point of where it comes from, but the underlying idea (a land whose creature-hood is real rather than cosmetic) is tidy type-line engineering, closer in spirit to Dryad Arbor than to any gag card.