Being cool has nothing at all to do with popularity, or nicheness. NOTHING.
Nicolis will never be cool because they are gopping and the transfers are on the wrong way.
Sub Zero?
I'd say an early Spesh Stumpjumper is possibly sub-zero. Curtis.
Cool?
Early FSRs because JMC rode one. Or a REAL Hei-Hei. Quite possibly Inbreds (Like Landrovers are)
Uncool?
Giant & Scott, because they look cheap and always have done. most Ti-frames because they try too hard. Anything with a hub gear.
Seriously Uncool?
Anything without 2 26in wheels. Jones (What a pile of tosh) Turner, because they change their suspension designs more often than thir underwear and give pish reasons as to why.