A bunch of gaming-related Valentines out there: The Most Romantic Moments in Gaming from GameSpot; romance across battlefields, species, and even the periodic table in One One Se7en, and Lorraine "Mehve" McLees' old Bungie valentines retrieved for nostalgic purposes by mrsmiley at Halo Babies.
UPDATE: Missed a few; a contribution in the HBO forum by Bluestone and another by Pak. Thanks Louis Wu.