ETA: All guessed (except for the mystery band, which was Lo-Fidelity Allstars, not exactly a household name, yes?) The winner is: philomel, with 14 correct; and a very close second is themoononastick with 13 correct! They both nailed some very obscure artists, so hat's off! And hey, dawnybee, you and I need to talk music more often! :)
Thanks to everyone for playing! I added links to video clips so you can see just who the hell some of the more obscure ones are! :)
KASABIAN: Performing "Club Foot" live on Letterman
Guessed by themoononastick
SNOW PATROL: "Chocolate" vid
Guessed by themoononastick and philomel. Incorrect guess: Beastie Boys
LOU BARLOW, of Dinosaur Jr., Sebadoh, and Folk Implosion: Promo clip of him covering Ratt's "Round 'n Round!"
Guessed by philomel
ARCADE FIRE: Rebellion (Lies) video. Too hard to march and play accordion? :)
Guessed by inthekeyofd, themoononastick, fosfomifira, uhzoomzip, philomel. Incorrect guess: Hot Club of Cowtown
Jimmy Eat World: Bleed American vid and aww, one more Performing "The Middle" (on Conan -- why can't I find the MTV vid? :/)
Guessed by quiet_rebel, dawnybee.
FIELDS OF THE NEPHILIM: "Moonchild" vid (Goth as hell! LOL)
Guessed by themoononastick -- I knew she'd be the only one would could possibly get this one!
AALIYAH: "More Than a Woman" vid
Guessed by quiet_rebel, arabella_hope, dawny_bee, inthekeyofd, uhzoomzip. Incorrect guess: Rihanna
MOBY "South Side" video with Gwen Stefani. This one always cracks me up. ;)
Guessed by eponine119, crowgirl13, quiet_rebel, dawnybee, inthekeyofd, themoononastick, uhzoomzip, fosfomifira, philomel.
SEMISONIC: "Closing Time" vid. Awww, I still love this song. *waxes nostalgic over the boy I had a crush on back then* (Every year needs a poppy, catchy sing-along-to-on-the-radio tune like this or "Shimmer" or "Hanging by a Moment," or "Meant to Live?" yes? :D)
Guessed by dawnybee, philomel.
Death Cab for Cutie: Ben Gibbard live solo acoustic on "I Will Follow You Into the Dark"
Guessed by philomel.
THE PIXIES: Live "Gigantic" perf. Kim Deal >>> everyone in the universe!
Guessed by dawnybee, themoononastick, fosfomifira, philomel.
NEW ORDER: "Regret" live video. (They're not known for appearing in their own videos, so I linked to this so you can see what they look like!)
Guessed by inthekeyofd, themoononastick, fosfomifira, philomel. Incorrect guess: Depeche Mode (Close!)
TEARS FOR FEARS: "Change" video
Guessed by dawnybee, inthekeyofd, themoononastick, uhzoomzip, philomel.
LED ZEPPELIN: (Heavily edited) performance video of "Whole Lotta Love" GUH!
Guessed by crowgirl13, dawnybee, inthekeyofd, themoononastick, uhzoomzip, fosfomifira, philomel. Incorrect guess: Aerosmith
BOB MARLEY: "Redemption Song" (live)
crowgirl13, quiet_rebel, dawnybee, inthekeyofd, themoononastick, uhzoomzip,fosfomifira, bachlava
ROBYN HITCHCOCK: "Madonna of the Wasps" (complete with eccentric intro) on Letterman. You'll probably recognize the song about a minute in.
Guessed by philomel
(There are no images out there of this group. I had to cap this from one of their videos. GOOD LUCK. Hint, the song has appeared in many films and shows. Oh, and they sound a lot like Band #1 or, you know, vice versa.)
LO-FIDELITY ALLSTARS: "Battleflag" video (I'm sure you recognize this song! "Tell me is it time to get down/on your motherfucking knees..."
Guessed by no one. (Not that I expected anyone to guess them. Incorrect guesses: Muse, one of the Gallagher brothers (right era and nationality!) But don't they sound a lot like Kasabian, if you listen to them, back to back?
THE CRANBERRIES: "Zombie" video
Guessed by crowgirl13, quiet_rebel, dawnybee, inthekeyofd, themoononastick, uhzoomzip,fosfomifira, philomel, bachlava
THE ROLLING STONES: Singing "The Last Time" circa 1965, Singing "Ruby Tuesday" on the Ed Sullivan Show in 1967
Guessed by crowgirl13, quiet_rebel, dawnybee, inthekeyofd, themoononastick, fosfomifira, philomel.
JOSEPH ARTHUR: "In the Sun" vid (Aww, I'd never seen this before!)
guessed by themooonastick, uhzoomzip and philomel