After a bit of googling around, I found this tumblr post:
Summary: the two scents people usually mention Tom possibly wearing are Farenheit by Dior and Armani Code. The above tumblr poster met Tom, smelled both colognes at a later date, and settled on the Armani. But - a lot of people do change his scent depending on the event or season, so it's very possible he uses both.
One of us is going to have to find him and smell him. For science.