aldeboran has a post about the Luck attribute in Goodman Games DCC RPG. If Luck is a one time pool of Save Your Bacon karma points does that change the way you play? Can it impact your fun knowing that you can thwart fate?
I see Luck being used in a lot of adventures as a Perception mechanic, but I really like what Purple Sorcerer does with it. The character with the highest luck is the one that usually benefits from activities - everyone searches a room and the jackpot goes to the luckiest character (instead of everyone rolling). Conversely, if anything bad is suppose to happen, the character with the lowest Luck is doomed. There is a beautiful example in the latest release, Lair of the Mist Men. If one character does something, the result causes 1d6 damage to the unluckiest character. There is a similar unlucky blow in DCC #70 (Jewels of the Carnifex). "Why does this always happen to me?!?"
I like that this puts a price on spending Luck. Like those Final Destination movies, you avoid falling to your death only to be constantly harassed by a cold and strangely vindictive universe.