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 normally go for parodies, but this would be the place to post the *Devil Went Down to Georgia (Washing Machine Cover): https://www.youtube.com/watch?v=u1hnBv12-uk
Another youtuber, Lord, added his own violin over it. It really improves it but distracts from the skillful contribution of Attaboy’s washing machine, so I’m linking both because I can’t decide.
Also of note, 2CELLOS’ rendition of Thunderstruck is incredible: https://www.youtube.com/watch?v=uT3SBzmDxGk
That is my favorite version of Thunderstruck, even more than the original.
(There was a really cool article I read ages ago that discussed how similar metal and classical music structures are. Have no idea where I found it.)