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Don't think about what YOU would appreciate...
If you put yourself in the shoes of someone making not too much a year, I think cash wins.
Some too expensive flowers that smell nice but will die in a few days or some cold hard cash that can actually be used to put gas in your car or pay off some bills or to take your SO out for a bite to eat.
The personal thank you note(s) are what make the gift personal. The cash signifies that you are serious about being grateful.
I remember being in grad school with student loans piling up, working a job that paid me $7 an hour and getting a $120 flower arrangment as a wedding gift.
I promised myself then that I would never give someone else a useless gift.