Mine would have to be the array! IntersectionObserver might be a distant…VERY distant second 
I like Function. But, hey, Arrays are cool too.
Boolean
Well maybe, or maybe not?
elm user?
Maybe Just Maybe (oh) Nothing ? 
this,
but is it always an object?
Not always, but it is most of the time, so that should count. ![]()
Date, because who doesn’t like an object that can get you dates :run_in_fear:
RegExp is pretty neat too.
I don’t have a favorite, but I like how random things can be combined:
Infinity.constructor(NaN) // NaN
NaN.constructor(Infinity) // Infinity
RegExp`Heya`
throw Symbol`hey`
(_ => Object)`${ void 0 }`
Hmm, looks like all these examples use functions… just sayin!

@senocular, I appreciate how you first “liked” my Boolean answer then “un-liked” it, very Boolean-esque. 
It’s been a while… are JS functions not objects?
Maybe I did, maybe I didn’t ![]()
They are. I said I liked functions. Then you come and show a bunch of functions, so I feel validated ![]()