Great Prophets for founding the shrines, though I did use one to get Theology quickly, which gave me Christianity. After the shrines are used, I think I only use them as specialists, or for starting a golden age.
Artist...haven't gone for a cultural victory yet, but they'd be useful for that. Are useful for preventing a just captured city from culture flipping to an ally or neutral civ.
Engineers are good for completing wonders - I saved up two to score me the space elevator, and nab me space race win in a very close game.
Scientists are good for Academies (figure +25% science to one city, vs the +11 to one city, vs the points towards a tech - simple math on which would be higher. If the city is making 100 beakers already, the +25% means 25 beakers...where that 11+75% from improvements would be 18-19 beakers)
I like golden ages...they give you a pretty healthy boost to production and research! Just don't go into anarchy during one.
Oh, and it's nice using one golden age to finish most've the Taj Mahal...back to back GA's ftw!