Here are a few to get things started:
Don Henley’s The Boys of Summer as an 80s synth tune
Bossa nova version of Crowded House’s Don’t Dream It’s Over
Reggae-ish version of Aretha Franklin’s Respect
A capella men’s ensemble version of Lady Gaga’s Bad Romance
I’m sorry, why has nobody mentioned the Jeff Buckley cover of Leonard Cohen’s Hallelujah yet? Bunch of heathens 🙂