I like the slightly stale smell of a large body of water. Sort of like the watery freshness plus all the seaweed flora, some dead some alive, combine into the smell of adventure.
Tobacco smoke, but only when it is someone else who's smoking.
Tea tree oil is just great.
I'm thinking of big International engines in trucks I've driven at various jobs. The imagery I get hit with when I smell them is sooty snow and black filth. And then I have the unforgettable secondary sensation of sitting in a musty cab with freezing feet while you're blasted with hot air. It's not all bad, I just really feel it.