For starters:
Sen. John Effin' Kerry (D-MA, now Secretary-of-State)
Sen. Tom Harkin (D-IA)
Sen. Richard Blumenthal (D-CT)
Each of whom, coincidentally, fought in Viet Nam. Or, at least, said they did. Turns out Blumenthal was never in Viet Nam...Harkin ferried planes between Japan and the Phillipines and was never in Nam...and Kerry, well, you know about him.
Not exactly the "proudly serving" nor the "honorable comrade in arms" sort...
Okay, so I struck out!
How about a present or past Obama Cabinet Member, other than the aforementioned Kerry?