Font-related support requests always seem to be present in support forums across the Web.
Below are the fonts that ship with OSX Leopard which are the minimum required by the system in order to function properly:
- AppleGothic.ttf
- Geneva.dfont
- Helvetica.dfont
- HelveticaNeue.dfont
- HelveLTMM
- Helvetica LT MM
- Keyboard.dfont
- LastResort.dfont
- LucidaGrande.dfont
- Monaco.dfont
- Times LT MM
- TimesLTMM
There are two rules that you must remember when dealing with fonts in OSX. First, never, ever, EEEEVVAAARRR disable, move, rename, spit-on or otherwise agitate AppleGothic.dfont or LucidaGrande.dfont. You're hosed if you do. Seriously!
Second, read up on fonts in OSX.
For more information about fonts in OSX and how not to shoot yourself when dealing with them, you can take a look at this fantastic (and lengthy) article by Kurt Lang; Font Management in OSX.
It appears that Kurt keeps this informative article updated with each new OS release, so you should probably bookmark it. It's by far the most in-depth, informative and balanced font article I've ever seen. If you find it useful, throw the guy a bone... his Paypal address is at the very bottom of the article.