Ferguson was reckoned to be the best shot in all of the British forces during the Revolutionary War. He also abided by several rules, the first of which was to never shoot a soldier who was unaware of his presence. So, yeah, sniping has changed a bit since then.
"Boo! Haha, but really, sorry."
In September 1777, Ferguson was involved in the Battle of Brandywine. He was busy, you know, killing people, when he saw two officers ride up a path on horses. Not being one to potentially let this opportunity pass him by, Ferguson quickly ordered his men to crawl up and ambush them.
"But wait!" you say, "What about his first and most important rule?" Well, Ferguson remembered that and changed his mind, thinking that shooting the officers in an ambush would be "disgusting." So instead, Ferguson did the only sensible thing a sniper would ever do: He stood up and made his position known to them.
"OK, now I just feel like a jerk."
Noticing him, one of the officers quickly galloped off, giving Ferguson the clearest shot yet. To quote Ferguson, "I could have lodged half a dozen balls in or about him, before he was out of my reach." But his own aversion to shooting a man in the back prevented him.
Later in the same battle, Ferguson was in the field hospital for an injured elbow when he learned that the officer he could have shot was General George Washington. Yeah, so if you really want the guy who saved the Revolution, look no further than the British sharpshooter whose conscience wouldn't let him take out the father of America.
But he was only known as "That what's-his-name who invented the Ferguson rifle."