I had to dig out the tux this weekend for a big soirée.
That meant dusting off my old Patek and slipping it under those tight French cuffs. I'm happy to say it's keeping very good time after 4 days running. 
I have others that qualify - thin, dressy, no date, black strap, manual wind - but I prefer this one for formal wear.
What watch do you use with a tux?
Cazalea