updated: 02/12/2007
Mission Impossible featured many disguises but these were more often achieved through illusion rather than makeup as such (though the makeup played a part in the illusion): in particular, it had some really good examples of the classic mask trick.
Cinnamon (Barbara Bain) is the one we all remember but it was Casey (Lynda Day George) who performed the best mask tricks.
Daniel C. Striepeke was the makeup artist for the series in 1966 to 1967: Bob Dawn was the series makeup artist from 1967 to 1973: he won the first Emmy Award for makeup in 1971 for the Mission Impossible episode The Catafalque (5.19).