Mine is lilacs, because there was a lilac bush at the bus stop that I used to wait at with my mom when I was a kid, it was my school bus stop and the public bus stop so we spent a lot of time on that corner and now when I smell lilacs I just immediately feel like a kid again.
Crudely burned gasoline in the late spring, only because it reminds me of being on my grandmother’s old army jeep and going down to the creek to swim.