My fiancé has a thing for my armpits and I like to use that to excite him. He loves to nuzzle them when we make love, and if I skip a day shaving, it arouses him even more. He travels on business a lot, so sometimes I'll "forget" to shave for 2 or 3 days before he gets home and drive him wild all weekend.
I've discovered he likes for other people to see my stubble, too. I'll wear a tank top to the store and reach for something up on a shelf, or in a restaurant I'll sit and tie my hair back, giving everyone a little armpit show. By the time we get home, he's just out of control!