When looking at men, I often notice their hands first. Specifically the size of them. I know, it wasn't the first thing I noticed on my Master (that was His eyes) but it was close. I was amused one of the first times my Master say Till Lindemann, the lead singer of the German rock band Rammstein. He joked that He saw an "ugly German guy"; I saw where their bodies are similar- Till has large hands too. With women, I notice long fingers. Of course with women, I tend to notice these things at inopportune times, like how I'm more likely to notice straight women.
But a large hand. A hand that can hurt as much as a paddle. I actually prefer a hand to most toys. Although one of the hottest lines- to me- that I've ever written is Simon from the Vala's Story series instructing some upper class slaves that "A leather glove is good when the spanking is for punishment, not for play.