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
The Slits - I Heard It Through The Grapevine
My Generation - Patti Smith
Pure Imagination - Fiona Apple
Wonderwall - Cat Power
Hotel California - The Cat Empire
Dolph Lundgren – A Little Less Conversation
The Gourds - Gin and Juice
William Shatner - Rocket Man
Snuff - I think we’re alone now
China Drum - Wuthering Heights
The Ukulele Orchestra of Great Britain - Smells Like Teen Spirit
The Ukulele Orchestra of Great Britain - Sweet Dreams
Hayseed Dixie - Bohemian Rhapsody
Hayseed Dixie - Roses
Richard Cheese - Gin And Juice
The Rock Orchestra - Chop Suey
Prime Orchestra - The Prodigy Medley
The Dmitry Butenko Orchestra - Freestyler
Balanescu Quartet - The Model
The Pogues – Honky Tonk Woman
Lemonheads – Mrs Robinson
Teenage Fanclub – Like a virgin
I was waiting for someone to mention Richard Cheese in this thread!
His version of Rape Me hasn’t aged terribly well, but my word is it great.
I used to regularly play Cheese stuff when driving my elderly mother places