The worst thing I've ever bought was my All Glass Aquarium stand.
My first tank is my current 75 gallon. I seen the nice wrought iron stand under a 55 at the LFS. I asked "can I get one of those for my 75?". "Sure Thing!" they answered. But they had to order it, and I had to wait to fill my tank.
A week later, it finally came in. The stand was nothing more than four peices of angle iron! NO decorative curved wrought iron on the sides like the one I seen under the 55. This thing looks like a cheapie garage shelf!
For some reason I brought it home. I filled the tank. Now I have a 75 gallon tank that wobbles when I drag my Mag-Float across the front of the tank. It's frightening! Cost me $110.