The Sims 3

(My own screen shot again. Seriously I love mods)

Title: The Sims 3
Creator: The Sims Studio (Ea Games)

Mechanics

Custom Content

Players are able to download endless amounts of high quality custom content and mods for free. This can be anything from hair, clothes and items to allowing teenage sims to get pregnant.

Interactions

Because the game relies heavily on narrative, interactions are the mechanic which allows this to happen. Sims form relationships, opportunities and enemies which are all determined through their interactions with other characters. For example, two sims can get married by using the flirt interaction. 

Aspirations

While there is no end goal or 'finish' in the game, there are aspirations. The player can either choose to meet these aspirations (becoming top at career, rich, having a family, being popular ect) and watch as their Sims live the ultimate life or alternatively the player can satisfy none of these aspirations and watch as their Sims lives turn to depression and chaos. When Aspirations are met however, the player earns points which can be used to purchase special items and unlock advantages such as getting promotions quicker.