I have several FileMaker Pro documents in my Dock for work purposes. All look the same withe their stock 'FileMaker document' icons, so when I try to find Chemistry 1B 2007 or Chemistry 1B 2008, it's not real easy. I could copy and paste a custom icon for each document, of course, but then I'd have to remember which custom icon went with which document.
Instead, I opened up TextEdit, set the font size to 20, and moved the cursor away from the edge. Then I typed:
Mac OS X Hints