Here is what I have kinda come up with for a FLARP game.
Each character has 6 conflicting stats, and one stat that conflicts itself.
-Advance, which would be speed. You catch things trying to Abscond with Advance.
-Avert, which would be defense. You block aggrieve attempts with Advert.
-Apprehend, which is sight. You catch things that are trying to Ensconce with Apprehend.
-Ensconce, which is sneak. You avoid being Apprehended with Ensconce.
-Aggrieve, which is attacking.
-Abscond, which is running away. You avoid Advances with Abscond.
-Actuate, which is persuasion. You persuade people with Actuate, and you also keep from getting persuaded with Actuate.
Each of these stats was figured out by rolling 7d6, with each player deciding which number went with each stat. The classes were decided by the player, and had no effect on the stats (although their abilities do!).
For each attack, you roll 1d8 + your Aggrieve stat. The opposing monster (or player!) rolls 1d6 + their Avert stat. Whatever number you get over their Avert roll is the amount of damage you do. All 'stat' based abilities are used this way, in fact. If using a ranged weapon, you roll a 1d3 + your Aggrieve stat.
Players each have Vitality, which are their hit points. Vitality is calculated by Aggrive+Avert. Once you lose all of your vitality is gone, you die. For each few battles you help your team win, you gain a level, and get some stat points to allot wherever you please. HOWEVER monsters do the same! So while you get more specialized in certain areas, so do they. You also have Power Points, which are spent to use Abilities.
Monsters are rolled the same way players are, with the Clouder deciding what stats go where. The Clouder is the "DM" so to speak, they are actually a member of the other team, and therefore are there to make it as challenging as they can. Though in this campaign, at least, the second team is actually nonexistant, and just assumed for the sake of RP.
Once you get your rolls, you make a class, with an ability you can make up, as long as it is reasonable. As you level up, you gain more Vitality and abilities.