I think that a good mechanic should solve a problem, help reinforce who the characters are, establish how the world works, and reinforce the genre that you are going for. I was very tempted to talk about the D6 roll try for low Mechanic but I’m going talk about something else that has made an impression on me.
My online group has been playing alien by free league publishing. The base system is not very revolutionary. It uses a dice pool, the dice used are six sided, and sixes are successes. Extra successes can produce better or additional effects. The dice pool is assembled based upon the attributes and skills of the character. Pretty standard.
However, various experiences in the game introduce stress. Each character has a stress tracker. Stress tends to escalate upwards, although certain things can reduce or eliminate it. Stress isn’t an entirely bad thing, as the player now adds a number of different colored six sided dice to their dice pool. Just like the harried characters in the alien & aliens movies, The characters in this game are paying more attention to what they are doing in their moments of stress and are more likely to succeed. However, should a one be rolled on any of the stress dice, This prompts a panic roll.
A six sided die is rolled and the characters current stress level is added to it. Make sure it’s consulted which gives you an idea of what the characters reaction is going to be. This varies from holding it together to trembling, to becoming so upset that they raise the stress of everybody else around them, to running away, freezing in their tracks, and other appropriate reactions based upon the genre. Eventually they are unable to successfully complete any tasks.
The game gives clear instructions not to roll too often as this will artificially escalate the stress level.
My experience with this mechanic is that really helps to reinforce the genre that the game is based upon. It’s not everybody’s cup of tea, but I have really enjoyed it. It certainly helps create the atmosphere of the movies.