A ridiculously simple system, so easy even a retard could play it. Invented on 8chan's /tg/ board.
Each character gets six stats. Each stat must be given a modifier from the set [-2, -1, +1, +1, +2, +2]. These stats can be whatever the player wants them to be; there is no set list of attributes or skills to use for stats. Any stat that isn't set for the character is at +0.
All challenges are rolled with 2d6 with the appropriate stat modifier added. On a 2 or 3, the character critically fails. On 4-6, the character regularly fails. On 7-9, the character succeeds, and on 10-12 the player critically succeeds. However, if the player rolls doubles, something bad also happens if the player succeeds at all, or something good if the player fails at all.