most annyong vocals...
hmm that makes it tougher
there's no way i can do justice in just a post, but i'll try to name as many as I can (so take this with a grain of salt)
really bad ones
D'yer Maker, Sweet Child O' Mine - Sheryl Crow
American Pie - Madonna
whateva P-Diddy or whatever he's calling himself now is up to...
Imagine, No Quarter - Tool
Imagine, Stairway to Heaven, Crimson & Clover - Dolly Parton
Behind Blue Eyes - Limp Bizkit
Take a Chance on Me - Metallica
Another Brick in the Wall, Word Up - Korn
Dock of the Bay, When a Man Loves a Woman - Michael Bolton
Harlem Shuffle - The Rolling Stones
Dancing in the Street - Mick Jagger & David Bowie
Let's Spend the Night Together, Alabama Song (Whiskey Bar), God Only Knows (a few others are borderline) - David Bowie
911 is a Joke - Duran Duran
Can't Help Falling in Love, Light My Fire, Every Breath You Take - UB40 (their Red Red Wine is okay & I Got You Babe with Chrissie Hynde isn't horrible , but it's not good either)
Smells Like Teen Spirit - Tori Amos
Sexual Healing - Soul Asylum
The End, My Best Friend's Girl - Nirvana
Ticket to Ride - Sonic Youth (like Nirvana's cover of the Doors' The end it's meant to be a joke, but still it's pretty horrible & not nearly funny enough either)
Paranoid - Megadeth
Suspicious Minds - Fine Young Cannibals
novelties (golden throats)
Lucy in the Sky with Diamonds, Mr. Tambourine Man - William Shatner
Proud Mary - Leonard Nimoy
really good ones
All Along the Watchtower, Sunshine of Your Love, Hey Joe, Wild Thing, The Star-Spangled Banner - Jimi Hendrix Experience
My Favorite Things, Lush Life, Like Someone in Love - John Coltrane
Twist & Shout, Dizzie Miss Lizzie, Long Tall Sally, Roll Over Beethoven, Act Naturally, Everybody's Trying to be my Baby, A Taste of Honey, Besame Mucho, Blue Seude Shoes, Money, Please Mr. Postman, Kansas City Hey Hey - The Beatles
Stand by Me, Be-Bop-A-Lula, Ain't that a Shame, Sweet Little Sixteen, You Can't Catch Me - John Lennon
The Ballad of Hollis Brown, House of the Rising Sun, Fixin' to Die - Bob Dylan
In My Time of Dying, Bring it on Home, When the Levee Breaks, Traveling Riverside Blues - Led Zeppelin
Black Diamond - The Replacements
Oops I Did it Again - Richard Thompson (much better than the original anyway)
whatever Brad Mehldau touches
Hound Dog, Blue Suede Shoes - Elvis Presley
Respect - Aretha Franklin
Cocaine - Eric Clapton (I Shot the Sheriff is just okay)
I Know There's An Answer, Into the Groove(y), Ca Plane Pour Moi, Within You Without You, Beat on the Brat, I don't wanna Walk Around WIth You, Simpsons Theme, Nic Fit, Superstar - Sonic Youth
Interstellar Overdrive (instrumental though), O Death, Wasted, I Love Her All the Time, Tusk - Camper Van Beethoven
The Man Who Sold the World, Where Did you Sleep Last night, Oh me, Plateau, Son of a Gun, Turnaround, Love Buzz - Nirvana (sunbeam & molly's are not bad, but not good either, etc.)
I Heard it Through the Grapevine, Susie Q, I Put a Spell on You - Creedence Clearwater Revival
Gloria, My Generation - Patti Smith Group
Who do you Love, Gloria, Back Door Man, Little Red Rooster, Crawling King Snake, Alabama Song (Whiskey Bar) - The Doors
Who do you Love - George Thorogood & the Delaware Destroyers
The Raincoats - Lola
Some Velvet Morning - Roland S. Howard with Lydia Lunch
Love in Vain, Little Queenie, Not Fade Away, Little Red Rooster /added

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Carol, The Last Time, Time is on My Side, Under the Boardwalk, You Gotta Move - The Rolling Stones
Dancing in the Street, Pretty Woman - Van Halen
Dancing in the Street, Louie Louie - The Kinks
Dancing in the Street, Hard to Handle - The Grateful Dead
Hard to Handle, Custard Pie (with Jimmy Page) - The Black Crowes
Heartbreak Hotel - John Cale
Feelin' Alright, With a Little Help From My Friends, She Came in Through the Bathroom Window - Joe Cocker
Voodoo Chile - Stevie Ray Vaughan & Double Trouble
Battery - Megadeth
Victoria - The Fall
(I Can't Get No) Satisfaction, Head Like A Hole - Devo
Crazy, Femme Fatale, Pale Blue Eyes - R.E.M.
Turn the Page - Metallica (to be fair, this one is good...Tuesday's Gone is not as good, but not bad)
Ring of Fire, Long Black Veil, Hurt - Johnny Cash
Those Were The Days, If I were a Carpenter (with Joe Nichols) - Dolly Parton
Crazy Little Thing Called Love - Dwight Yoakam
Tainted Love - Soft Cell
Books of Moses, It's Alright with Me - Tom Waits
Sea of Love, Wild is the Wind, I Found a Reason, Paths of Victory - Cat Power
Sea of Love - The Honeydrippers
Rocket Man - Kate Bush
Hide Your Love Away, Masters of War - Pearl Jam