WordNet sense 1 (the quantity that can be held in a mug):

mugful

WordNet sense 2 (a person who is gullible and easy to take advantage of):

chump, fool, gull, mark, patsy, sucker, fall guy, soft touch

WordNet sense 3 (the human face (`kisser' and `smiler' and `mug' are informal terms for `face' and `phiz' is British)):

countenance, kisser, physiognomy, visage, Phiz, smiler