They are not cheap but I love the Squash Air CS-X3 Refillable Air Freshener Dispenser
. It is hard to describe the scent but it's like a fresh, hint of citrus, clean scent. Everyone seems to love it when they get in my car and it lasts a few weeks. After a few weeks I put it in my arm rest and when you want that scent again, just open the arm rest which works for roughly a year.
Greg @ DI
p.s. If your wife/gf won't kill you the Chemical Guys Stripper Scent - Smell of Success
is also very popular