Edit: A bit of munging from the web page later...
For Americans and British/Western Europe, the passports you want are Burkina Faso, Benin and Senegal. They will bring your passport power level up by 13 points to 168 (American) and 170 (UK) and give you visa free access to Cote Divoire (Ivory Coast), Mali, Iran, Congo, Niger, Benin, Nigeria, Liberia, Central African Republic, Sierra Leone, Guinea, Chad, Ghana. In reality these countries may not allow dual citizenship! Benin and Burkina Faso however do recognize dual citizenship while Senegal does not. (http://www.multiplecitizenship.com/worldsummary.html)
The highest power level you can have as a dual citizen is 170. Any combination of these three African countries and Western European nations will achieve this. So the most powerful dual citizens are mostly West African migrants.
Now for triple citizens, the highest possible power is a whopping 178. There are a few combinations that do this, involving those 3 African countries, plus Russian Federation, Singapore, Japan and Turkey. For example, Turkey/Japan/Senegal, Burkina Faso/Russia/Singapore, Japan/Benin/Turkey. So it looks like the path to ultimate power is sadly blocked for those of us in the USA and Europe, and in fact, the most powerful dual citizens cannot become the most powerful triple citizens. On the other hand, Senegal/United States of America/Malaysia will get you 177, nearly as good.