Another way to deal with the whole concept of luck is simply to have a stat called “luck” which gives a +X (probably rolled like all other stats) to everything (but that would be a bit exessive — maybe certain rolls, or usable X times per game or something)

Just my 2 CPs

1) Science fiction game (forgot the name, sorry). All rolls on a d10. Any “1″ is always a minor failure, but gives you a “luck point” to add a single +1 to any one future roll. Function : avoids getting too many automatic failures in a game session (you add a “+1″ future “1″s… or allows a minor compensation for bad luck.
2) Marvel Superheros “Karma” either adds to your rolls (providing some of those huge “KaBOOM!” manoeuvres when you need them most. BUT it is also your fund of experience points. Effect : you can be super-effectvie in combat BUT at the cost of slowing your progress… (one or two pernicious effects there…) Also killing people loses you all your karma instantly (including any your team-mates pooled into the teams mutual-support fund of karma), except chunks put aside before play (and unusable during play… ) to finance character progression. Points awarded are based on heroic acts accomplished. Points can be lost for bad behaviour, too.
3)Starmont(Homebrew system) : Celestial Karma points. a) roll twice the usual number of dice b) a permanent +1 to a stat (max 1 per stat per scenario), (ie. = experience points) c) automatic minimum success d) survive (comatose) an unsurvivable bunch of damage e) atempt to implore a Celestials intervention (very rarely works… except in utterly critical-to-world moments). 2-6 points per scenario based on good role-playing/ objectives achieved/ teamwork /Celestials pleased, etc.

The first thing that comes to mind is that these would quickly become dominant factors, and they are all positive, which is what you would expect from the expenditure of a feat slot. They also seem pretty powerful, even for feats. Nothing wrong per se with that. So they are trying to simulate a person who has good luck because of feats, and are not an overall-neutral system, which is what I’ve created.

I would consider the two fairly compatable, but would state that you couldn’t use Luck Points on a reroll granted by a Luck Feat. Taking one of these feats would mean that there is one category of roll less than everyone else sucking up luck points from your pool, so your luck points would go further. However, I would permit the GM to expend HIS luck points affecting the outcome of a reroll – so that he could maintain the original outcome, at the expense of cutting a great swathe through his luck pool, if it was vital to the dynamics of storytelling that he do so.

Once again, though, there remains the caveat that my proposed system has not been tried in an actual game, whereas these feats have (I hope) been thoroughly playtested.

I’m listing them in the following format

Luck
Feats
Prerequisites Benefit

Advantageous Avoidance
Character level 3rd, any luck feat
Expend luck reroll to force foe to reroll critical threat
confirmation, or three luck rerolls to force foe to reroll attack

Better Lucky than Good
Character level 6th, any two luck feats
Expend luck reroll to treat natural 1 on attack as atural 20 instead

Dumb Luck
Character level 6th, any two luck feats
Expend luck reroll to treat natural 1 on save as natural 20 instead

Fortuitous Strike
Character level 6th, any luck feat
Expend luck reroll to reroll attack, or two luck rerolls to
reroll damage

Good Karma
Character level 3rd
Expend luck reroll to redirect attack against ally to you

Healer’s Luck
No prereqs
Reroll amount cured by healing spell

Lucky Break
No prereqs
Reroll Strength check to break item or burst door

Lucky Catch
No prereqs
Reroll Balance, Climb, or Jump check

Lucky Fingers
No prereqs
Reroll Disable Device, Open Lock, or Sleight of Hand check

Lucky Start
No prereqs
Reroll initiative check

Magical Fortune
Caster level 3rd,any luck feat
Expend luck reroll to reroll damage dealt by spell, or two luck
rerolls to reroll caster level check

Make Your Own Luck
Character level 6th, any luck feat
Reroll a skill check

Miser’s Fortune
No prereqs
Your items get +5 bonus on saves; expend luck reroll to force foe
to reroll a sunder attack or Str check to damage nearby object

Psychic Luck
Manifester level 3rd, any luck feat
Expend luck reroll to reroll damage dealt by power, or two luck
rerolls to reroll manifester level check

Sly Fortune
No prereqs
Reroll Hide, Move Silently, or Tumble check

Survivor’s Luck
Character level 9th, any luck feat
Reroll a saving throw

Tempting Fate
Character level 6th, any luck feat
Reroll stabilization check, expend luck reroll to avoid being killed

Third Time’s the Charm
Character level 3rd, any luck feat,
Reroll again with Luck domain granted power Luck domain

Unbelievable Luck
Any luck feat
Gain two luck rerolls and +2 luck bonus on worst save

Victor’s Luck
No prereqs
Reroll critical threat confirmation