I stumbled across an interesting RPG called Kapow! that features a dice mechanic I've not seen before: powers are assigned 2 dice, like d10, d10, or d8, d6.  You don't add the dice together, though: you roll both and take the higher of the two results.  Not having a good head for probabilities and stats, I'm wondering if someone could explain how that affects outcomes.  For example, when you roll d8 twice and take the higher result, does that change the average roll result?  How much of the time will d8, d8 beat d8, d6?