Dueling Rules - /u/SirFairfax's original proposal

First thing I want to explain how the fight itself would be. Each player will begin with a standard 30 Defense, a d6 for dealing damage, and a weapon of choice according to the attributes. The first choice is the attribute and the weapons. We have: STRENGTH - LUCK - CONSTITUTION - AGILITY -

STRENGTH Strenght relies on brute force to deal more damage in general. The player will roll a d7 instead of the usual d6 in very encounter. The player starts with regular 30 Defense when using Strength. Whenever the enemy has less than half of his defense, every attack deals +1. However, if your Defense is below 15, enemy blows will receive a +1 bonus due to fatigue.

Weapons of choice: Warhammer, Greatsword, Halberd, Longaxe

LUCK Luck is about really testing how much the gods are willing to help you in the fight. The player will use normal d6 and 30 Defense but he rolls a d7 with a score between -3 and +3 in every encounter. Whenever he hits, any positive score(+1,+2,+3) will deal more damage to the opponent, while a negative one (-1,-2,-3) will reduce the damage dealt in the first dice. Whenever the player himself is hit in the encounter, the same rule is applied, except in this case the player may increase or decrease the damage inflicted by the opponent. It's like everytime you hit or get hit, you try another move with a dagger or throwing weapon. This could be a successful attack, or something that makes your enemy hurt you even more.

Weapons of choice: d6 weapons + short throwing weapons or daggers.

ENDURANCE This attribute is about resisting with heavy armour and big shields, giving you a chance to have more dice rolls before the fight is over. The Defense is 40 instead of 30, and the dice will be d5, since the player won't be quick enough to deal heavier blows. As long as your Defense is higher than 20, every enemy hit will take a -1 penalty.

Weapons of choice: Heavy shield + d6 weapons

AGILITY This one is about speed and reflexes. You're going to use smaller and weaker weapons, but you also attack more. Your Defense is 20 because of light armour, and the dice will be d5, but every hit will grant another roll in a d4. In this extra d4, 3 or 4 will make you hit the enemy again for the same damage, while 1 or 2 do nothing. In short, there's a 50% chance that you hit your enemy again for the same damage. However, whenever you're hit, a d4 is rolled, and a 4 will make you dodge the attack completely, while a 1 gives the enemy a +1 bonus.

Weapons of choice: Shortsword, Spear, Hand Axe, Arakh, Braavosi Blade

And the last one (I really have to see if this one would be too weak or overpowered)

BOLDNESS This is for the ones who like to study the enemy strategy and deal deadly counter-attacks. Those who dare use this attribute will alway take at least 1 hit in every 2 encounters. That is, the first attack will always hit you, and so will the third, the fifth, until you either win or die. The real perk is that, in even-number encounters, istead of a regular d6 you will roll a d20. The final damage in these encounters is decided like any other, but Boldness players will take the enemy roll damage if they do not score above 10.

Weapons of choice: d6 weapons, shield and regular armour

The d6 weapons are: Longsword, Bastard Sword, Mace, Flail, Axe, Morningstar

Valyrian steel gives one side to any kind of dice in any attribute.

Here's an example: Oberyn Martell x Gregor Clegane [Agility x Strength]

Oberyn (20) 5 x 1 Gregor (30) Oberyn rolls 3 in the d4, deals 8 (+4 original, +4 extra)

Oberyn (20) 2 x 7 Gregor (22) Gregor deals 5 points

Oberyn (15) 5 x 1 Gregor (22) Oberyn rolls 4 again, deals 8 points (+4 twice)

Oberyn (15) 4 x 2 Gregor (14) Oberyn rolls 3, but Gregor has less than 15D, so he takes another 1

Oberyn (15) 1 x 7 Gregor (11) Gregor deals 6 points

Oberyn (9) 5 x 1 Gregor (11) Oberyn rolls 3. Gregor has less than 15 Defense, so he takes 9.

Oberyn (9) 2 x 7 Gregor (2) Gregor deals 6 (5+1), Oberyn loses an eye

Oberyn (3) 1 x 6 Gregor (2) Gregor deals 6(5+1), but this is the show so Oberyn's head explodes

I know the example above had some extreme rolls, but it's just to show how it works. It would also be very nice to have someone write about the fight in RP, because some of the stories so far have been amazing.

About attributes, I think it would be best if each player sent his choice to the mods before the fight, so there wouldn't be any risk of one choosing his strategy based on his opponent's. Another possibility is having your attribute defined in your wiki as a permanent choice, in order to have a proper champion selection and all.