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
EDIT: This has been great, everyone. Thanks to everyone for all the terrific links and for introducing me to a number of artists I wouldn’t have heard of otherwise. Seriously, the online rabbit-holes have been thoroughly enjoyable–even it I stayed up a bit too late a number of times.
Worth it.
Their version of Straight Up is genuinely one of the best things I’ve ever heard.
As for their cover of Goodbye Earl, the only criticism I have is that it’s too damn short.
I love the Gimmes immensely, and am disappointed that I had to scroll down so far to find any mention of them. Their guitarist is in one of the world’s biggest bands ffs!