As D&D has evolved over the years many rules and mechanics have been tweaked and changed in order to make the game better. I think one of the greatest improvements was when actions points were introduced with the Eberron Campaign Setting back in 3e D&D. They began as bonus to your d20 roll. Expending an action point meant a good attack became a great attack. With 4e D&D the action point was changed and this good idea became a great idea. Now you actually got another action when you used an action point. Awesome!
Recently I’ve been thinking back to how Wizards of the Coast described the original action point mechanic. One of the reasons it was introduced was to add an extra level of excitement to encounters. This was your chance to have your character do something truly remarkable. You suddenly gave greater consideration to trying new things that were over the top and spectacular.