Morgan at Cowpens.
Yup. He didn’t exactly play by the rules either. Having your troops “run away” to sucker the enemy into attacking your ‘remaining’ troops, only to have them circle the battlefield and hit the enemy from the flank with cavalry mounting a counterbalancing charge from the opposite flank, was just not done back then.
Having the ‘skirmishers’ aka ‘sharpshooters with rifles’ snipe the officers first when possible and then execute a fighting retreat to the militia lines rather than stand unsupported on-line and get pounded by the Brits probably contributed more to the success of the operation than any other part as after that point the British seem to have suffered a progressive breakdown in leadership and were unable to recognize what was being done to them.
Tarleton’s arrogance didn’t hurt either.
Other examples I actually like better for unconventionality are Fort Watson (”Hm, attacking the Fort on line doesn’t seem to be working - let’s put a scaffold up in the air outside musket shot and have our guys snipe the crap out of the Redcoats on the walls”) and Augusta (”Well, attacking on line doesn’t seem to be working here either - that scaffold idea worked really well at Fort Watson, let’s do that again... only this time let’s put a cannon up there!”).
The British *really* took offense to those two losses.