I know it's an old fashioned variety, but the white ones are pretty fragrant, much more than that 'primrose' lilac. Seems like the bigger the flower the less fragrant it is.

I think President Grevy is one of the most fragrant -- and Ludwig Spaeth.

Many are fragrant in different ways, though. The koreans and persians have a nice scent.

My mom has a miss kim lilac..she loves the smell, but I can't stand it, it smells like plastic to me.