I'm sure all of us are attracted to a variety of features in the opposite sex/same sex. But what physical or behavioral feature pretty much snags you at first glance?
For me, any guy/girl with black hair and light eyes can get my attention regardless of how good looking they might be. I'll pretty much stare at that person until I'm satisfied looking =P As for a behavioral feature... I'm instantly attracted to someone I see making all his/her friends laugh... but not in a dorky hands-in-pocket/searching-for-attention/nervous kind of way, but leaning back, smiling and telling his/her story with confidence, ease and animation.