I know that people have had cool fonts for everything.. Are these included in the theme the have set or can you have a different font for the whole phone?
You can have a different font for the whole system or for only certain parts. I use the [free] Cydia tweak BytaFont. There are thousands of fonts to choose from - hardest is deciding which one to use.
And he's, some theme makers create their own fonts and they are installable (usually via BytaFont).