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
Kate Bush’s Wuthering Heights feels like an entire different song when sung by Cécile McLorin Salvant
I’m also very fond of Oingo Boingo’s version of I’m the Walrus, I like how they do the laughs with the guitars.