Very Cool
Mustaches.
Mustaches, like my own, very cool.
Sideburns
Well, anything the King made famous has to be a little cool! Cool.
Plaid miniskirts
On the right kind of girl, very cool.
Airboats.
Cool.
Network optimization. 
Nerdy, but cool.
Snake Plissken.
Snake is the coolest.
Normcore.
Not sure if this is cool as it is so cyclical. I seem to recall a movement called the blands that essentially tried to do the same thing but my Google fu came up empty. I vote not cool.
Fedoras.
Not cool unless you’re Indiana Jones.
Han Solo.
Cool. And he shot first.
The Royal Family.
Cool. I didn’t really understand why Britons tolerated the crown until I went to England and experienced the culture first-hand.
Next: Disney
Sometimes but rarely cool (except Pixar, now a division thereof, which is cool far more often than not).
Damn straight.
Fezes.
Anything that Dr.Who and Peter Sellers would wear must be cool!
silk dinner jackets.
Cool.
Bow ties.
In Indianapolis at least: not cool.
Wearing your clothes in the droop.
VERY uncool.
Hillary Clinton.
Positively frigid.
Unboxing videos.
Not cool. It’s never anything I can afford…
Omega Watches
Cool.
Swiss Army knives.
What’s not to love? Cool.
Salad with dressing on the side.