Here is my favorite combo, although the civs in the game that feature this combo aren't the greatest (Americans):
- Expansionist: I picked this trait mainly because it can serve as Scientific and much more. By this I mean that if you know what you are doing, those scouts can bring in plenty of free techs from goody huts; most likely more than the three that you would get from the Scientific trait. Also, you can get settlers, cities, warriors, money, and who knows what else from the goody huts. And barbarians are less aggressive towards you (so Firaxis says).
- Industrious: Industrious is another great trait because it speeds up my initial growth and gives me an early lead. As you may have noticed from my Expansionist comments, I like to gain an early lead and then hold it throughout the game.