I decided some time ago that the alignment system doesn't quite fit with the style of play that I tend to encourage with my group. I find too often that players tend to use alignment as an excuse to do or not do something ("but I'm chaotic neutral!"). It isn't that the system is inherently flawed any more than other systems, it just isn't what I want. It doesn't feel right. After all, Commander Vimes (of Discworld) is obviously both Lawful and Good, but does some awfully non-lawful-good things from time to time.
So for most characters, they get to scribble in a quick belief statement. It doesn't have to be complex, but it should sum things up and be a guideline for the player. There are no mechanical penalties for straying from this path, and in fact it encourages a character to change and evolve through a lack of limitation, but there are bonuses in the form of Karma (a karmic bonus for being yourself).
Some characters, though, have a set of tenets they must follow. Knights and Paladins have a code of honor and conduct - failure will result in a loss of status. More restrictive, however, are the clerics. Clerics gain power through their gods, and the gods are picky, and a cleric that disobeys the faith is going to find themselves quickly bereft of spells and special abilities.
Dungeons Are Darkness
When a character does something that is outright wicked, they will gain a point of Darkness. Acts of valor and unselfish goodness can reduce this amount, but that isn't quite as likely. Spending vast amounts of time in true dungeon can begin to warp a character's mind. Carelessly practicing the arcane arts will open holes in the mind. Too much Darkness and the character begins to become Hollow.
Darkness points aren't like Dark Side points of Star Wars (WEG rules ... d6 SW and Paranoia? Come on!) but rather like a slow an definite descent into the madness like Sanity Loss in Call of Cthulu. All of that, but less terrible. We don't want PCs dropping like flies just for getting a bit rowdy. It is more a measure of how close the character is to falling into the abyss. It won't have any affect until they reach 20 points, at which point they may be lost to the dungeon and become a minion of evil ... and probably a rather juicy NPC as well. The player rolls 1d20+level, the GM 1d20+character darkness. If the GM wins, NPC time. If the play wins, they don't go off into the wilderness of wickedness, but get a chance at redemption.
0 - a pure innocent
5 - average city dweller
10 - a seasoned soldier of many wars
15 - an veteran adventurer that has seen enough
20 - Most Bad Guy NPCs
25 - crazy wizards
30 - goblins and orcs
40 - trolls and giants
50 - Liches, demons, and the like
75 - Patchwork Lords, The Goblin King
100 - Evil gods such as The Endless Void of Bile and Blood Who Consumes All Children
In short, a player may indicate that his character is seeking redemption, and will be provided with some opportunities to make themselves better people and reduce their Darkness. This is some serious role playing waiting to happen. This might be a big fancy quest, or retiring for 1d3+1 years to work at an orphanage (which is easy except the other characters will continue to advance and an adventurer that does not adventure is bare an adventurer at all), or a multitude of small things where the right choice (a path to atonement) are the least beneficial to the character. The GM will cook up some juicy stuff. No matter what, each time the character gains another point of Darkness above 20, they'll have to check again. Watch your Ps and Qs!