My favorite MM performance is in the technicolored noir film, NIAGRA; which actully makes a great follow-up to DON'T BOTHER TO KNOCK.
No doubt that my favorite MM flick is SOME LIKE IT HOT, her fuzzy end of the lollipop scene gets me everytime.
Ater those:
GENTLEMEN PREFER BLONDES
THE SEVEN YEAR ITCH
BUS STOP
O. HENRY'S FULL HOUSE (still not out on dvd)
HOW TO MARRY A MILLIONAIRE
Has some studio exec been smarter in the 1950's, she could've done a remake of ROXIE HART, and done it very well.
MM does have that delightful "After You Get What You Want" in THERE'S NO BUSINESS LIKE SHOW BUSINESS, and then there's that terrifically over the top "Heat Wave" in the same film.
George Chakiris can be glimpsed in the latter number, but in GENTLEMEN'S "Diamonds are a Girl's Best Friend," he's much easier to spot.