A long plug for appliances that a shorter plug can't reach. This is a good quality, figure 8 moulded plug that is properly fused. Not a cheap(er) DIY one that has been made from core wire with ends attached on.
I wall mounted an LG 3D LED TV and was apprehensive about using an extension, but cutting the original power cables invalidates warranty so I went for this one. I have now been using this for about 2 months with no problems.
It is plugged into my TV and run along 3 metres of cable trunking with 3 HDMI,1 AV, 1 optical and 1 ethernet cable (so its pretty cramped in there). The cables are going round corners (chimney) so the wire is probably a bit squashed and stretched, so I would say it's being tested. I have no problem with the power and it has not interfered with the quality or signals of the other cables in any way.
I would recommend this if you are in a similar situation with a projector, console or TV. Don't invalidate your warranty by cutting your wire, try this on for size. It's a much better option.