The Czech letter ř is the ultimate linguistic boss fight—half rolling r, half zh sound, and entirely out to confuse foreigners. Even language prodigies (and some native speakers) tremble before it. Want a challenge? Try saying: "Tři sta třicet tři stříbrných stříkaček stříkalo přes tři sta třicet tři stříbrných střech." (Three hundred thirty-three silver fire nozzles were spraying over three hundred thirty-three silver roofs.) Good luck, if you can do it, you deserve a medal!

A stamp dedicated to the letter ř, alternatively to the cress plant, which is called řeřicha in Czech. The stamp could depict silver fire nozzles too, as they're part of the well-known tongue twister.