Dungeons & Dragons introduced Luck feats and the Fortune's Fool prestige class late in 3.5. Although the flavor of it has them surviving in day-to-day life based purely on being incredibly lucky, the mechanics just let you re-roll dice a lot.
The Eberron Campaign setting has the Archfae known as Fortune's Fool. The archfae of Eberron are creatures of story, and the Fool's story is to be forever stumbling into a new disaster, which she invariably emerges from unscathed. Her arrival usually bodes ill for those unfortunate enough to be around her, though sometimes others can profit from the chaos that follows in her wake.
Everway, which uses a modified Tarot deck as a game play mechanic, has an Alternate Character Interpretation of The Fool: a cross between a court jester and a wanderer. The Fool is free to do or say anything and get away with it, because no one takes him too seriously, and he's not tied down with responsibilities. This doesn't imply stupidity or luck. More like "Jack of all trades; master of none." Some forms of "real" Tarot reading portray the whole deck (or at least the picture cards) as representing The Fool's journey to enlightenment.
Mage: The Awakening associates the Acanthus Path with the Tarot card of The Fool. Members of the Path have a natural affinity for Fate magic, meaning they can get really lucky.
Unknown Armies has The Fool as an avatar, where you can be happy go lucky, find the right item at the right time, avoid damage by accident, be in the right (or wrong) place at the right (or wrong) time. It can be incredibly powerful at times, but it's always dangerous to be around, since all that conveniently avoided damage has to happen to someone. Notably, it damages your connection to the archetype if your mental stats go too high - you need to literally be a fool to be the Fool.
