NIPAJIN stands for Niemand ist perfekt, aber jeder irgendwie nützlich (Nobody is perfect, but everybody useful in some way). It is a light-weight rules system currently used for several one-shot RPG adventures.
Character creation is very short. The player notes what the character has done in his past life. Those notes will later be used for task resolution purposes. Besides those notes, every character has five dice (d4, d6, d8, d10, d12). The player selects one die as his resistance die. The other dice are his action pool.
When the outcome of an action must be determined, the GM declares a target number according to the difficulty of the attempted action. The player then selects one die from his action pool and rolls it. He also may get a modifier depending on his character background. If the modified roll is equal to or higher than the target number, the action succeeds. The die is removed from the pool. The action pool is only refreshed after all dice are spent.
In a conflict, the character selects two dice in each round: his action die and his reaction die. The size of the action die determines initiative. Those dice are used for all actions during a combat round. An attack works like a skill check with the action die. Only that the defending character rolls his reaction die and the attacker must overcome the resulting value. A hit causes a wound. Wounds are counted using the resistance die. It starts with 1, and a character is incapacitated if the die is at its maximum number and the character receives another wound. Characters that have only one die left may select freely if the die is used as action or reaction in this round. If no dice are left in the pool, the character must spend a round to take a breath before his pool is refreshed.
A scenario may also allow the players to select "effects" like spells, super powers, etc.
NPCs may withstand more wounds than the normal player, and they may also use a d20 in their pool if they are very powerful.
The system is not designed for long term campaigns and thus has no explicit experience rules. If it is used for this purpose, it suggests that the GM rewards the characters with additional effects and better modificators depending on the experiences in the previous adventures.