Wasteland Viper

Bloodrush is the mechanic that lets a creature card spend itself as a combat trick without ever committing the body to the battlefield, and welding deathtouch to that pump is what makes the math punishing. Cast for its single green mana, the snake is a 1/2 with deathtouch that polices the ground: anything that attacks into it dies for one point of damage, so its toughness only has to survive long enough to deal that point. Kept in hand instead, it converts into a green pump aimed at one of your own attackers, discarded after blocks to grant +1/+2 and deathtouch until end of turn. The deathtouch is the live part of that trick: lethality scales independent of the buff, so once the boost lands, any single point of combat damage through a declared blocker already kills it, no matter how large. The +1/+2 is insurance that the boosted attacker survives the swing and connects, not the kill condition itself. The friction lives in the choice of window, with the same green mana paying for either use. Resolve it early and the snake taxes every attack the opponent might consider; hold it and it punishes the defender after they have committed a blocker, turning a confident trade into a one-sided loss. A one-drop that gives green a clean way to make combat lethal in a color that usually has to scrap for its removal.