You MUST keep SOME copy of Helvetica active at all times! It doesn't have to be the OSX Helvetica, just some Helvetica.

You might want to keep Arial and Verdana active for viewing webpages.

If your using Classic then you'll need to keep the city fonts available:
Charcoal
Geneva
Chicago (probably don't need it anymore, but what's it gonna hurt?)
Monaco
New York (same as Chicago, but might as well keep it)

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