What national wonders are best for an OCC? The limit is 6 in ROM, and you shouldn't need the Globe Theatre, since the Olympic Games cures happiness problems earlier without counting towards the limit. (there is no world wonder limit)
I ran down the list and took some notes on what appeared to be the most useful ones; I think that Oxford, National Epic, National Park, Ironworks (with iron), a military boost (Secret Army Base is best if you can hold out that long, otherwise West Point is probably more useful than Heroic Epic on any speed but Snail), and a resource provider that is limiting you are the best bet. Of course, it is very situational, since apart from Oxford and National Epic none of them are really mandatory.
Mandatory:
National Epic - more great people
Oxford University - The 3 scientist slots are very valuable, and even +50% science is still so good to be necessary.
Mandatory in Some Situations:
National Park - loss of coal, but will likely save you at least 10 health. Watermills are probably always better than forest preserves (even with a vacation resort as well), so you won't get many specialists, though. If you don't have coal, it has no downside.
Ironworks - probably worthwhile with just the +25% production from iron, great with iron and coal
Temple of Osiris - requires Kemetism (probably means founding it unless you are very lucky), but +25% food with wheat (at Writing!) very useful
Resources:
Steel Mill - +25% hammers, probably not with Iron Works; can't be after National Park
Filing Factory - ammunition can generally be bought, though it may be expensive
Aluminum Factory, Cement Mill - probably buyable when necessary, cement is only needed for skyscraper and hydro plant
Brewery - probably harmful, you aren't happiness limited
Nanite Lab - too late in the game?
Rubber Plant / Chemical Plant - 15% production isn't bad, rubber can also be bought
Military:
Heroic Epic - probably not necessary
West Point - great generals can compensate
Red Cross - probably have super-medics in all stacks without this
Royal Tournament - probably not enough mounted units
Secret Army Base - late game, but very powerful - +100% espionage, plus heroic epic, plus half of west point
Science:
Supercollider - +50% science, but late
Computer Center - +50% science and 1 free tech, but even later
Not Useful:
Any with continent-wide bonuses - not good enough for one city
Any with income bonuses - unlikely for money to be limiting factor, +50% isn't that much
I ran down the list and took some notes on what appeared to be the most useful ones; I think that Oxford, National Epic, National Park, Ironworks (with iron), a military boost (Secret Army Base is best if you can hold out that long, otherwise West Point is probably more useful than Heroic Epic on any speed but Snail), and a resource provider that is limiting you are the best bet. Of course, it is very situational, since apart from Oxford and National Epic none of them are really mandatory.
Mandatory:
National Epic - more great people
Oxford University - The 3 scientist slots are very valuable, and even +50% science is still so good to be necessary.
Mandatory in Some Situations:
National Park - loss of coal, but will likely save you at least 10 health. Watermills are probably always better than forest preserves (even with a vacation resort as well), so you won't get many specialists, though. If you don't have coal, it has no downside.
Ironworks - probably worthwhile with just the +25% production from iron, great with iron and coal
Temple of Osiris - requires Kemetism (probably means founding it unless you are very lucky), but +25% food with wheat (at Writing!) very useful
Resources:
Steel Mill - +25% hammers, probably not with Iron Works; can't be after National Park
Filing Factory - ammunition can generally be bought, though it may be expensive
Aluminum Factory, Cement Mill - probably buyable when necessary, cement is only needed for skyscraper and hydro plant
Brewery - probably harmful, you aren't happiness limited
Nanite Lab - too late in the game?
Rubber Plant / Chemical Plant - 15% production isn't bad, rubber can also be bought
Military:
Heroic Epic - probably not necessary
West Point - great generals can compensate
Red Cross - probably have super-medics in all stacks without this
Royal Tournament - probably not enough mounted units
Secret Army Base - late game, but very powerful - +100% espionage, plus heroic epic, plus half of west point
Science:
Supercollider - +50% science, but late
Computer Center - +50% science and 1 free tech, but even later
Not Useful:
Any with continent-wide bonuses - not good enough for one city
Any with income bonuses - unlikely for money to be limiting factor, +50% isn't that much