Standalones:
1.) Stonehenge
building Monuments takes time, too much time for the reward.
With stonehengei save 90 hammers in each new city.
ALSO it places a monument in each newly conquered city, who are devoid of all culturistic building. With stonehenge, i get 1 instand Culture, + modifiers (stele works wodners here)
2.) Great Library
For a philosophical leader, this is a must.
For everyone else, its a should.
3.) Hanging Gardens
Population-boom extreme.
Either whip them or have them work, doesnt matter, your economy gets a massive shove upwards.
Just make sure to found 3 cities the turn before you complete it.
Combo-Contenders:
(the following wonders work best in combination with others, but are not game-breaking on their own)
Great Lighthouse, Colossus, Statue of Zeus, Temple of Artemis, Parthenon, Pyramids.
If you have lots of coastal cities, the first two are more important than all else. Statue of zeus is nice to have just for the reason that you are not effected by it.
Temple of Artemis is heaily underrated i think.
Philo-leader gets 10 points out of it (2 from the temple, 3 from the priest, 100% bonus)
With parthenon/pacifism..... do the math.
You may notice the absence of Pyramids in the top 3.
Well, i dont see them as crucial as before, since i mostly rely on hereditary rule for happiness, and seldom run SEs.