Gun.Smoke

Gun.Smoke is a shooter arcade game released in 1985. It was ported to the NES in 1988 The game, which has a Western theme, centers around a character named Billy Bob, a bounty hunter who is after vicious criminals of the Wild West. This game is considered to be one of the hardest games Capcom ever made. Despite the name and theme of the game, there is no connection to the Western TV series of the same name (1955-1975).

Original description (US box):

Gun.Smoke by Capcom takes you back to the days of the Gold Rush, to a small, bustling mining town of the Old West. Ruthless gold-stealing bandits are terrorizing the townsfolk and it's up to you to stop them!
The thieves are notorious killers, and when they challenge you to a draw, they're playing for keeps! Although your gunslinging prowess is legendary, this may be the toughest High Noon you'll ever face. But you've got to stand your ground - this town ain't big enough for both you and them!

Instructions

Enter - start (pause);    Arrows - move;    Space - equip weapons;    Esc = exit fullscreen;
Z - fire to the right;    X - fire to the left;    Z + X = fire straight ahead;

You can change keyboard settings, save (F5) and load (F8) the game.
Put your mouse over the game and choose your settings, you can also play the game in fullscreen.