Always been partial to Louis Prima, being from Vegas and all....
From 'Hey Boy, Hey Girl"
Another funny one: Billy Idol in The Wedding Singer.
Jack White as Elvis on Dewy Cox: Walk Hard (classic)
You mean like Dick Dale and Stevie Ray Vaughn in Back to the Beach? Or Arch Hall jr. in Eegah. The Ramones were in Rock and Roll High School. Guitar Wolf and the Royal Pendletons in The Sore Losers.
Another one: L7 in Serial Mom. Thanks Antonio for posting that clip.
Another one: Jeff Healy in Roadhouse.
Oh I was going to say Strawberry Alarm Clock in Psych Out too. I love that film. Aren't the Seeds in that too? The weird funeral scene?
The Pretty Things are in What's Good For The Goose, cringey scene but I really like this song
Oh yeah, Gene Simmons in Runaway