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.
I love the smell of burning firewood. There’s lots of homes that have little bonfires in their backyards during the summer months. Admittedly, I keep my windows open during the summer just so I can smell it, it’s oddly relaxing.