remembered another one
Walk up to a girl and tell her you have a magic watch that can tell you anything you ask it. And then say 'do you want to know what it says toi me now'.
And when she says what you say 'it says you're wearin no panties'
And she'll go 'well it must be wrong becauyse I am wearing panties'
And then you tap the watch and say 'damn thing must be an hour fast'