As a student of ancient, medieval, and Napoleonic tactics, hit-and-run is a very good tactic. It was used by everyone, from the Mongols to Jeb Stuart. It is not my favorite, because I find it a cowardly un-manly tactic to be used only by terrorists, savages, and barbarians.
My favorite medieval one is the Roman turtle formation and the Greek phalanx/pike wall formation. The turtle formation worked very well, blocking arrows and if I remember correctly, scaring horses. It was vulnerable to rear attacks, though, so it didn't always work perfectly.
The Greek phalanx/medieval pike wall is my favorite. A well-trained regiment of pikemen is nearly invincible; marching forward destroying everybody in their path. With a few swordsmen in the back to turn away attackers, it was one of the most powerful moves on the battlefield. The fact that they were used until the 1700's should show you their usefulness.
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