He was a vampire, she was a slayer, but all the good sense in Sunnydale couldn't keep the two apart. With the mother of all human-vampire trysts, Buffy (Sarah Michelle Gellar) and Angel (David Boreanaz) set the standard for forbidden love.
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Meredith and Derek? Lois and Clark? Bo and Hope? We've nominated 25; see 'em all, then go to our poll and make your pick!