For me it would have to be "The Beastie Boys" and "Semisonic"
Probably "Weird Al" Yankovic. His only popular music these days are the music videos and his newest "Al-bums". Everyone has seen "Eat it" or "Fat" but there are great pieces such as all of his polkas!
I love his Polka songs, they are ■■■■ catchy.(made Coldplay sound good lol)
Though i found Mandatory Fun a bit bland, but thats mostly due to the songs he sampled.
It's a power metal band that made some of my favorite songs. If your into that sort of thing, check these out.
(had to get an alt. link for that last one, the album cover is kinda NSFW and that's a big no no here)
It look's like I'm too mainstream to listen to any of this... Welp!
Prog bands in general. I'll single out Emerson, Lake, and Palmer because they've become kind of a whipping boy for prog's excesses, but IMO they're still really good.
A few tracks:
The band will never become popular as they refused to be played in radios in their Dogma04-declaration and their albums are nigh impossible to find. Also international fame is out of question because the songs are in Finnish. It's the ultimate band for hipsters.
That's a seriously cool looking armadillo.
My Fave band Royal Republic really, really could use a boost in popularity.