son of a gun
From Longman Dictionary of Contemporary Englishson of a gunˌson of a ˈgun noun [singular] American English spoken 1 ENJOY/LIKE DOING somethinga man you like or admire – used humorously Duke, you old son of a gun, how are you?2 ANNOYa man that you are annoyed with Somebody go tell that son of a gun we’re all waiting here.3 DIFFICULTan object that is difficult to deal with – used humorously4 → son of a gun!son of a gun!son of a gun! spokenSURPRISEDused to express surprise → son of a gun