This is an excerpt from "Font Management in OS X" by Kurt Lang
For More information, please refer to: http://www.jklstudios.com/misc/osxfonts.html

The following lists are the fonts you must have for OS X. All are located in the /System/Library/Fonts/ folder.

OS X, 10.7 Lion
The minimum System folder font list for OS X, 10.7 is as follows:

OS X, 10.7.2 Lion
In the /Library/Fonts/ folder:


In the /System/Library/Fonts/ folder and the ProtectedFonts folder:


OS X, 10.7.3 Lion
In the /Library/Fonts/ folder:

In the /System/Library/Fonts/ folder and the ProtectedFonts folder:


OS X, 10.8 Mountain Lion


With the exception of the above list, MarkerFelt.ttc in Snow Leopard, and AppleGothic.ttf in Mountain Lion, all other fonts in the /Library/Fonts/ folder can be removed (refer to the next statement concerning iLife and iWork). The following fonts are also located in the /Library/Fonts/ folder. While the iLife and iWork apps will launch without the following fonts, the supplied templates use them. Apple suggests these fonts always be available for these apps. If you do not use the any of the iLife or iWork apps, you can remove these fonts. Most of these fonts in Leopard, 10.5 and earlier are .dfonts. Also in 10.5 and earlier, Chalkboard and Chalkboard Bold are separate fonts. In 10.6 and later, they are combined in the TrueType Collection, Chalkboard.ttc.

OS X, 10.9 Mavericks

Apple has shifted fonts around again in Mavericks. The Avenir, Palatino and Optima fonts, which were in the /Library/Fonts/ folder in Mountain Lion are now in the /System/Library/Fonts/ folder. The system Thonburi .ttf fonts have been combined into a single .ttc font.

Apple Gothic no longer appeared to be a required font, but a change in 10.9.2 has brought it back. The Messages app now fails if this font is missing. The default font for Notes is now Helvetica, so MarkerFelt is also no longer needed. You can easily change the default font for Notes back to MarkerFelt if you wish. Leave MarkerFelt on your system if you prefer to use that font.

The keyboard viewer has changed in Mavericks to use the font AppleSDGothicNeo. It will display very strangely if this font is not active.

Be extremely careful when removing fonts in Mavericks. There is no longer a ProtectedFonts folder. If you remove a critical system font and delete it, it's gone and will need to be replaced from a backup, or by reinstalling the OS if you have no backup.

In all previous versions of OS X, the loss of Lucida Grande would make your system unusable. What Mavericks does differently as a form of font protection is to use the first available system font (not including Apple Color Emoji) for the menus. I had already minimized the fonts in my System folder, so when I removed Lucida Grande, Mavericks switched to Courier, which was next in the list. If I removed that, the menus switched to Geneva. Mavericks will continue to move down the list of available fonts alphabetically.

The minimum fonts recommended for Mavericks in the /System/Library/Fonts/ folder are:

Fonts updated in 10.9.2

Apple Color Emoji.ttf, AmericanTypewriter.ttc, ArialHB.ttc