While I don't normally use them in my games, looking over some old work of mine regarding a Dark Sun/Iron Heroes game, I came across a bit of altered mechanics for them that I think merit mentioning in this blog. The normal action point rules are pretty standard from normal 3rd edition, but I did add a mechanic from White Wolf's Vampire: The Masquerade for players to regain points.
Each PC starts the game with an action point pool of 5, and the pool expands by 1 per every level.
The character may spend points(as many as he wants as long as he has the points to spend), and gain a bonus to any given roll. The player may only spend the points before the DM determination as to what the result of the roll is.
Each character chooses a Nature/Demeanor archetype(presented in the V:TM book) at character creation, and any time the character does something that would result in V:TM characters regaining a Willpower point, they instead regain an Action point.