Non-targetting attacks, a simple yet highly effective system of giving orders to your troops, requiring food/drink to maintain morale, Dueling Tournaments, Open tournaments etc etc. And that's all before you got to the incredible fighting system. Joining a Faction to fight for betraying them or advancing to become King, starting your own Faction and recruiting new members, and the overall lvl of detail in the game was very nice.
A truly epic game where you start as a lowly nobody, and have to fight/recruit/conquer your way up. I absolutely fell in love with the original Mount and Blade.