Love 'em...
I really like APs. I have been using some type of Hero Points/Action Points for some time, but the "turning point" for me was the release of Grim Tales. I have taken the AP mechanic from GT, home-brewed it a bit and come up with the result in the attached file.
I would also consider adding "Emulate Feat" to this list as well...
~ OO
PS - I Also like the "Exploding Dice" variant as well...where you get to roll an additional action die if you roll a "6" on the d6. There is not limit to the number of times you can do this...as long as you keep rolling sixes. This helps defray the "it isn't helpful if I roll a low number" problem...since there is always a chance you will get an exploding dice. This can also be combined with the level-based "roll more dice and bick the best"...so levels 1-6 would roll 1d6, levels 7-12 would roll 2d6 and levels 13+ would roll 3d6, taking the best result. Clearly, the chances of rolling a 6 and qualifying for exploding dice ramp up quickly under this system.