I like Lyndsay Louie. She is a sim that shipped with Sims 2: Apartment Life and she married Don Lothario and Chastity Gere in two of my games. I found the non-committal sims found domestic bliss with her. The whims for affairs hardly came up, and marriage was a happy memory. Lyndsay is a bohemian sim.
La Shawn Cameron is another great sim. I had her marry different generations of Ottomas. Once Tommy and in another game she married the unborn twin, who the mother started the game pregnant. La Shawn is a goth chick who grows into a successful businesswoman. Unlike other sims I've played, I had no problem moving her up the career ladder. La Shawn is a tech sim.