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.
Star Jasmine (aka confederate jasmine, not a true jasmine). Reminds me of my time in San Jose where I saw them often. It has a lovely sweet smell that reminds me of nutmeg.