Fireforger's Puzzleknot

Two pings of damage from one artifact, split across two windows and paid on your schedule. The first arrives the moment it lands, the second waits behind a sacrifice cost you trigger when you want it. That staging is the entire function: an artifact entering and an artifact leaving are both events that other cards reward, and this one manufactures both at your convenience for a small total investment. The damage is almost incidental to the engine value. Its size is modest enough that it rarely answers anything that matters, which is the trade the design accepts: the payoff is in the two triggers and the colorless body, not the pings. Preloading one ping and parking the second behind makes for a deliberately slow burn package, tuned for decks that count artifacts rather than count damage. As red removal it is hopeless; as a flexible source of two enter-and-leave events that happens to clear a token or finish off a planeswalker on its way through, it does honest work for the colorless-matters builds that gave it a home.