Cool: Steel and ti Kona's from the '90's
+1
Seriously uncool: Yeti 575, any SC (except Superlights and only if they look well ridden), Marin Alchemist (argh!), Whyte full sussers, Any singlespeed (there is no cool way of explaining to non MTBers why you only have one gear)
Uncool: Orange 5 (I own one) – the latest victim of glowing mag reviews pretty much killing anything left-field and cool about it. I'd still buy another though. Any Commencal full susser. Lap Spicys and Zestys (See Orange 5).
Cool: Whyte HTs, Intense Tracer (just)
Subzero: DMR Switchback, Orange ST4, Cotic Soul/Soda BFe, Cove Handjob/Hummer/Stiffie