this one works every time:
You know what?...You remind me so much of my mom.
good for a knee to the groin any time.
but my all time personal favorite goes like this:
::walking up to a pretty lady standing at the bar or somewhere::
"hi there gorgeous, you look like you need a place to sit down. Let me clean a place off for you".
::Proceed to lick your fingers and wipe around the outside of your mouth::