Does she like the Marx Brothers? Get her a DVD of Horse Feathers.
Secretary: The Dean is furious. He’s waxing wroth.
Prof. Wagstaff [Groucho]: Is Roth out there too? Tell Roth to wax the Dean for a while.
How about something personal that could only come from you? Or more specifically, from your ears?
jnglmassiv:
I’ve been to the Crayola factory. Hardly any smell at all.
As to the OP: How about putting her present in a pinata, and she’ll take some whacks at it?
Or a letter in which you wax romantic?
Are you artistic?
Or sadistic?
Write it in Crayola Crayons.
Take a trip to Colonial Williamsburg and stop in the nearby Yankee Candle factory store.
…Does she like Fine French Film…? 
OK – it’s not romantic but your question reminds me of these
from various visits to zoos and science centers as a kid.
Or you could look at a different website and get her something silver: https://anniversariesbyyear.com/16thanniversary.php
Something having to do with Mr. Miyagi?
Chocolate-covered grasshoppers!
A new pair of shoes or boots and some shoe wax?
I have a cute statuette made of wax. Maybe you buy her something like that.
An expensive bottle of wine that’s been sealed with wax.
My wife likes a musician/band called Wax Tailor. I didn’t know that the 16th anniversary is the “wax anniversary”. Good to know, as my next anniversary will be our 16th! Maybe I’ll get her tickets.
Mold-A-Rama! Not wax, unfortunately.
Check out this awesome WBEZ piece:
Give her a 100,000 Colombian peso note (approx $28 USD), the obverse of which feature thePalma de Cera - the wax palm, Colombia’s national tree.
Use that as a hint for a vacation destination in Colombia. Thermal spring spas near Santa Rosa are a day trip away from the Cocora Valley, the native habitat of the Palma de Cera. This area near the city of Pereira offers many options for an eco-vacation.
An encausticpainting. Or lots and lots of honeycomb.
Would that work? 