German Reiters - armoured, pistol-armed cavalry - were dominant on the battlefield for a while in the late 16th century.
Their most effective tactic was the famous "Caracole."
They would form up in a block, 8-20 ranks deep, 30-100 files wide.
They would ride up to the enemy at close range. The first rank would fire their pistols, wheel off to the right or left and go to the back of the formation to reload. While they were doing this the next rank had already stepped forward to fire another volley. And so on.
They could do this because it was possible to reload a wheel-lock pistol while moving on horseback (with enough training) and because the preferred target for this was stationary pike blocks.
Must have been pretty scary if you were a pikeman: constant rolling fire at close range, and if you move to attack them they run away.
It wasn't invincible though. Infantry arquebusiers and musketeers could fire back, and determined lancer cavalry could break them if they were willing to absorb a pistol volley and still charge home.
Later cavalry, especially Swedes and Poles, would retain the sabre and lance and keep acting as melee shock cavalry.
But for a while it worked.