I've recently been reading the excellent Grim World game supplement for Dungeon World and the Fate roleplaying system; if you're a fan of either game then I highly recommend that you have a look at it since there are some excellent classes and new ideas listed that can add a lot to any game. A particular section that caught my eye was titled "Dungeon World/Fate hack" and it suggested porting some elements from the Fate system over into the DW game; essentially the player picks three 'hindrances' (similar to the 'trouble aspect' in Fate) when generating their character and, whenever the GM uses the hindrance to cause them complications (as with 'compels' in Fate) the players receive a luck point that can be used to re-roll dice, gain bonuses or add improvised elements to the setting.
Effectively the hack is porting trouble aspects, GM compels and fate points into the Dungeon World setting and doing so very simply with minimal additional complication (always a positive thing in my view); it got me thinking as well that, aside from the actual effects of spending the luck points, the ideas behind this are pretty much non-system specific. I think that this idea could be used to great effect in other games, encouraging players to think a little about what causes their characters problems in their life and it also allows the players to have a little more input into the game setting, for example, if one of the players takes 'in debt with the mob' as a hindrance then you can reasonably infer that they are interesting in seeing some stories involving organised crime.
I'd love to think that people will give this idea a try in some other games, if you do, let me know how it goes :)