I'm not too keen on black nailpolish but I had a pretty good experience with glittery nails:

Yesterday I went to a house/pool party to celebrate the fourth of July. My girlfriend had painted my toenails a bright sparkly blue the week before, and I had completely forgotten about it until everybody at the party started commenting on my feet. Random girls would open up to me: "Hey I like your nails" *teasing* and then I would explain yeah my girlfriend painted them and I would get the "Aww that's so sweet." Guys made jokes about it of course, but I was pulled into three or four pictures of just me in the middle of a bunch of girls showing off our nails poolside... so it worked out pretty well.

The glittery nails were a DHV for several reasons:
1. It showed I was comfortable with my masculinity and sexuality.
2. It showed pre-selection. It let everyone know I was some degree of taken without having to say a word, which made all the other women interested.

If you're going for the black nailpolish to look goth, or intense, or artsy or whatever, that might backfire on you... but if you go the opposite direction and make yourself look goofy and have a good sense of humor about it you can really build yourself up.

~Antithesis