i'll start things off by mentioning the ones i like and why:
in nomine : the d666now what i like about both these systems is the fact that, on a meta-level, there's this extra element of excitement; the dice rolling mechanism itself becomes more harrowing a thing for the tabletop gamer to do. i mean, this could easily be done by, say, announcing that any natural 20s rolled on a d20 is a critical success automatically and any 1s are auto failures.. but somehow it's just not the same. maybe it's just me, but i think it beats the regular garden variety dice conventions.
since it's a game of angels and demons (not the dan brown book, no), having the number 666 factor in is pretty apropos. what happens is you roll 3d6. two of the d6s are added together to come up with a sum to compare to the difficulty. the remaining d6 is the check digit - the degree of success or failure for that task check. what's more, depending on what side of the War you're on, there are special Intervention rolls: there's, of course, the number of the beast (rolling 6s on all 3 dice) and the Holy Trinity (roll all 1s). each one could spell out a divine or infernal intervention which, in game turns, is equivalent to a critical success or critical botch (again, depending on which team you play for).
feng shui : the open roll
in feng shui, doing skill checks requires rolling 2d6, two dice of differing colors. one represents a positive number while the other represents a negative. these two are summed up (with the result being positive or negative) and added to the player character's stat (+skill) and then compared to a difficulty. the amount over the difficulty value (the outcome) and figures into such things like additional damage inflicted. what's more, for every 6 that's rolled (positive or negative), the die is rolled again, adding to the original value by that amount (this can theoretically go on forever, resulting in insanely high or insanely low numbers). should two 6s be rolled (boxcars), the dice are rerolled. should this second roll result in a success, it becomes a critical success.. some GMs rule that botched rolls after boxcars result in critical botches as well.
comments? ideas? donuts?