Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
This is a typical Spaghetti Western, made by Italians, shot in Spain, and dubbed into English. It uses a lot of western cliches: bank robbers fleeing to Mexico chased by the law; gunfights; death by quicksand, and, fortunately for me, a gratuitous snake scene.
John Webb is guiding insane bandit boss Klaus Kinski through the desert to Mexico along with his men, two horses loaded with boxes full of stolen gold, and two women hostages. They stop to rest and a young woman named Sandy, who is attracted to Webb, lies down on a blanket. We see a snake very slowly crawl towards her blanket. Webb sees it, aims his pistol, and blows its head off. My hero. Sandy wakes up and screams. (Spoiler alert - she ride off into the sunset with him at the end.) We don't get a good look at the snake after its head is supposedly blown off, but the head appears to be still on the snake and though we don't see it move again, it clearly moved between when Sandy rolls over to see it and when she is comforted by the other woman, so I don't think it was really injured.
This is basically the typical dangerous snake scene found in many westerns for no good reason other than to have the hero kill something to prove his worth. It barely advances the plot, but audiences expect it I guess. I'm always hoping to see this kind of scene because they let me sarcastically mock the filmmakers. But what makes this snake scene really cool is that the snake is not a type of snake I've ever seen in a movie. I'm not sure what kind of snake this slow-moving, fat, and wrinkly thing is. Spaghetti westerns rarely use rattlesnakes since they are not found in Spain, but they typically use native Spanish snakes or at least fake rattlesnakes. This one sort of looks like a File Snake, an exclusively aquatic snake from Northern Australia and islands to the north, but it might be some kind of North African Sand Boa, which makes more sense. Let me know if you know what it is. At any rate, it's definitely one of the silliest and least dangerous-looking snakes on screen.
You can watch the whole movie on YouTube. The snake scene starts at 58:17