Here's a Dark Knight version batman mask made of mostly duct tape. It was made to enter in a county fair "duct tape creations" contest. It won $15 dollars.
It's fairly rough, but maybe it'll inspire somebody.
Step 1: Custom fit for your head
To start, I laid out lots of strips of duct tape on my cutting mat, and sliced them into various sized smaller strips. Using a plastic grocery bag to protect my head, I started putting tape all over my head to get my personal head-shape. I trimmed off extra plastic as I went. My head was sweating like crazy, as plastic and duct tape don't breath very well...