There IS! There are many great built-in symbols in the fonts included in Mac OS X. Here's how to use them:
1. Go to system Preferences, select the 'International' control (under Personal)
2. In the 'Input Menu' tab makes sure Character Palette is checked.
3. You should have a little flag next to the time in your menu bar..
4. Click on it and select 'Show Character Palette"
5. Drag some Special Effects Text ("LETTERING") into your comic. The input box appears.
6. You can now drag a symbol from the character palette to the text input box!
This gives you access to hearts, arrows, office symbols etc., even the pirate sign!
(These steps might be slightly different due to various OS X differences)