At Knifepoint [OTJ-193] Foil - Outlaws of Thunder Junction

As long as it's your turn, outlaws you control have first strike. (Assassins, Mercenaries, Pirates, Rogues, and Warlocks are outlaws.)
Whenever you commit a crime, create a 1/1 red Mercenary creature token with ": Target creature you control gets +1/+0 until end of turn. Activate only as a sorcery." This ability triggers only once each turn.