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.
A band on TikTok did an emo cover of Rascal Flatts’ What Hurts the Most that is pretty good.
It ended up on a compilation album Country Goes Hardcore that has some interesting ones. I like Ever Since Eve’s emo cover of Take Me Home, Country Roads.