Worst grooming tips or tools?

Since we always see a lot of really good grooming tips and tools reccommended here, I thought it would be fun to see the flip side of the coin. And maybe help someone avoid the pitfalls of some of the "not so wonderful" grooming tools and tips. The worst thing I ever bought was a grooming brush that attached to a drill. In theory, the idea was that the spinning round brush would groom your horse in half the time and with half the effort. In reality, this thing would tangle up in a mane or tail and before you could get it loose, you had a drill banging on your horse before you could get it untangled. And even if your horse did not freeak out when it tangled, you still spent hours getting it loose (it was like it was designed to tangle hair, not groom). I saw more wrecks happen with this gadget (me included). I used mine one time, and into the garbage it went. So lets hear it. What is the worst thing you ever bought for grooming yoru horse?