Vintage T-Shirts

This one has been done for sure, but still may have some profit potential.  

You go to thrift stores to look for T-Shirts that have old dates on them and look "vintage" and cool.  You pay fifty cents for the T-Shirts, and sell them for much more on Ebay.

The trick is getting a steady supply of cool T-Shirts, but the upside is the incredible profit margin you achieve.  I mean, you could mark them up at least eight times what you paid.