Actually, I'm partial to AVGAS, but Jet A does have a great smell too.
My favorite smell is whatever it is that my girlfriend smells like, which is probably a conglomerate of all the different stuff that she uses, i.e. lotion, perfume, etc. I commonly refer to that scent as "girl." After a good cuddle session, I've got that smell all over me, and I love it.
Fresh cut grass, (golf)
Aspens and pines in dry, summer air (the mountains,)
Stale coffee smell in commercial jets
Burnt coffee smell in FBOs
(even though I don't drink coffee)
The ocean (even though I live in BOS
, I prefer the West Coast for ocean related pursuits)
I love the smell of a brand new Sectional Chart. I always take a huge wiff...