Yes, you can use other fonts but you might not want to do so. The choices of fonts for formatting text in your store are the basic fonts which are included on all computers by default. If you chose a font that was not installed on a users computer, ie something only you have installed then although it would look nice to you it might NOT look good to your customers who did not have that font. It would be shown to them as an alternative courier font which is usually not very nice looking.
If you do NEED to use a more fancy font not listed there the best way to do so would be to make the words into a graphic. Graphics are saved as pixels and therefore the font does not need to be installed on each users computer for them to see it properly.