Triton Shorestalker

Unblockable on a one-drop is one of blue's oldest tempo bargains, and this is about as stripped-down as the deal gets: a single blue mana buys a body that will always connect, with nothing else bolted on. The lineage runs through evasive one-mana bodies like Slither Blade, creatures whose entire pitch is that they enter, attack, and never trade in the red zone. That permanence is the whole point. A 1/1 dies to everything, but it cannot be ambushed in combat, which makes it a reliable carrier for whatever you want delivered face: an equipment, a curiosity-style draw enabler, a pump spell that turns the swing into real damage. The Merfolk Rogue type line does quiet work too, slotting the creature into two of blue's recurring tribal shells without asking the deck to bend around it. What it is not is a threat on its own; the toughness keeps it honest, and any deck running it accepts that the creature is a chassis, not a payload. The job is consistent damage and reliable triggers from turn two onward, and for one mana it does that without conditions, spectacle costs, or activation fees.