So, "X" was hard for Meta MTG as well. There were some obvious choices, but since I am only showcasing cards that I actual own, the selection was quite limited. Then I remembered this card in the foil section of my collection: Xantid Swarm (Scourge).
I was shocked to see that not only is this foil close to the $20 range, but the regulars are a few bucks themselves. The foil I could maybe understand due to scarcity, but the regular's price leads me to believe it's actually played at some competitive level. It has a pretty cool ability. But which deck? I don't know. But here is my "X" for the entry!
Have you ever played (or heard of) with Xandit Swarm? If so, what deck do you use it in? What format, if any, if Xantid Swarm played in?