Lately something has been coming between you and your boyfriend. No, it's not his laundry habits--he hasn't left dirty socks on the floor in weeks. It's, well, his facial hair. He thinks his beard/mustache/goatee/mutton chops look cool. You think otherwise. You definitely don't want to hurt his feelings, but you do want to convince him to stop the follicular follies. In other words, you want him to shave--ASAP.
Drop both subtle and not so subtle hints. Tell him that his beard scratches your face when the two of you kiss or ask whether his employer has a mustache policy.
Find pictures of him before he grew the offending facial hair. Remark upon how handsome he looks in those photos. Muse aloud about how much you love a clean-shaven man.
Appeal to his vanity. Compare his looks to those of a stunning celebrity, adding, "I mean, you looked like him before you grew that beard."
Attend an event that might reasonably require him to lose the facial hair. Perhaps it's your grandma's 80th birthday party--and Grandma thinks that men with facial hair look unkempt. (You can say this even if your grandmother thinks no such thing; just make sure she's in on the plan).
Leave high end shaving products--rich shaving cream, designer aftershave, super soft shaving brushes--in his bathroom. Perhaps the temptation will be too great for him to resist.
Compromise. Maybe there's something that bugs him about you, too--although he always swears that you're perfect and you're inclined to believe him.