Use these scripts as templates, modify the values to fit your specific Western setting (steampunk, weird west, post-apocalyptic), and watch your players or audience lean forward. Because they aren't watching two people shoot. They are watching two worlds collide.
[MECHANICAL VALUE CHECK: Both roll for "Initiative." The Assassin has +3 Speed. But the Sheriff has +5 Precision (only hits vital areas).]
Sheriff (Public order) vs. Assassin (Chaos as a weapon).
SHERIFF: I know who you are. Jim "The Crow" Harkins. You killed the mayor's wife for fifty dollars.