TinEye's ability to find multiple copies of the same picture online is very useful when you're hunting down where an image has been used. You can also use that facility for finding shopping bargains by identifying online retailers selling the same product.
This suggestion comes to us courtesy of reader James:
TinEye reverse image search is not only for finding memes! It can be used to find items being sold for cheaper prices with a different description online.
For products with a highly specific name (such as motherboards), a text search is likely to produce better results, but this could be useful for clothing, decorator items and other less precise searches. If you find a useful bargain this way, tell us about it in the comments. Thanks James!