HDMI Cable

eBay can get you some really great deals on A/V cable, especially HDMI, which are absolutely required if you want to connect a HD video player (PS3, BluRay) to a HD television. But, one thing that people will try to tell you is that you will get much superior video quality out of a cable that costs three times as much.

Read enough about consumer reports and you'll know that average joes and videophiles were unable to tell the difference.