Sleeper Dart

Two mana buys a cantrip that leaves an object behind, and that object is the whole point. The card you draw pays for the artifact immediately, so the two mana is never wasted, and what remains is fodder: a permanent that costs nothing to keep around and ticks up whatever count-the-artifacts engine you are building toward. When you eventually spend it, the sacrifice clause hands its target a delay rather than removal, stranding a tapped attacker out of its owner's next turn without killing it or tapping it down. That is a softer effect than it looks, and the softness is deliberate: this is disruption you get for free on top of an artifact you were already happy to play. The activation also feeds any death-matters or graveyard payoff on the way out, so the value splits across three moments (the enter trigger, the standing artifact, the sacrifice) rather than front-loading all of it. A plain card-drawer like Divination replaces itself and then some, netting extra cards but leaving nothing on the battlefield; this one draws right away, keeps a permanent in play, and converts into targeted tempo whenever you need it. Modest, but coherent: built for decks that care how many artifacts they control and reward the moment one of them dies.