From my gardening experiences to date, that would be Gardenias at the top of my list. UT at Austin has a huge bank of gardenias planted at the front of the Tower base that when in bloom are intoxicating when you walk to classes. I used to go out of my way in gardenia season to route my campus walks by those things. My second favs would be roses, in particular, Blue Moon roses being at the top of that list. Never EVER smelled a rose with such an intense scent.
