I've always been fond of Rufus Wainwright's version of Leonard Cohen's "Hallelujah" but kd Lang knocked it out of the park last night for the Olympic opening ceremonies. Shivers ran up and down my spine. NBC is vigorously protecting its copyright of the Olympics, so here is the link. It is well worth watching, you can feel the emotion she puts into singing it and you know beyond the shadow of a doubt that she is not lip syncing while she delivers the best rendition I've ever heard.
If you don't want to install the Silverlight whatever on your computer, here is kd singing it at the 2005 Juno awards, another impressive performance.