Dick in a box
Not sure how this could work with ladies.
put on eyeliner and compose a lip sync/dance routine to the track Valentine by the Get Up Kids. One key element is that during the line "will you be my/valentine" you point limp wristedly at your beloved at 'you,' and at yourself for 'me.'
play videogames in your pants until 2 in the morning when you get a teary/angry phonecall. Reply with "I thought we agreed, like, y'know, corporate bullshit, and stuff." Works for both girls and chaps.