The Killers - Sweet Talk - Is off their B-side record: 'Sawdust', but is for mine their most consistent song. Mr. Brightside would be their most famous.
Muse - Citizen Erased - Off their sophmore album, it's a bit of an epic with contrasting tones through out and almost takes you on a journey. I don't know about most famous, but I'd say Plug In Baby is their signature song that goes off at concerts. Knights of Cydonia is also well worth checking out.
Foo Fighters - Everlong - Got to go with nqcowboy with this pick. They've got a really good library of songs the Foo Fighters, even if a couple of their last releases were really commercial but to me Everlong stands out above the rest as a rocking love ballad. The video also earns points too.
Queen - March of the Black Queen. Gah! Had such a tough time picking this or Play The Game which to me is basically everything you could ever like about Queen condensed into 3 minutes. March of the Black Queen on the other hand rivals Bohemion Rhapsody as an epic and personally I'd have to take Black Queen. I think the lyrics are better and the solos just rock that much harder. However, if I was to pick a signature track, it'd be Bohemion. Considering it performed well in two different decades reaffirms my position.
The Beatles - Across The Universe - Such a hard choice between this and Hey Jude but I find there's something more beautiful about my choice that just tips it in my choice's favour. I'm also a bigger Lennon fan so that might have something to do with it too. Most famous would be a difficult pick, I'd probably go with Let It Be, which seems to be the gate-way song.