Now, I know this one is too young to sex. This is just for fun. 15 day old olive egger (Isbar x Marans). Seems to have much thicker legs than the other chicks from the same hatch date.
I do find that roosters seem to have a more rounded comb at a young age, and hens have a flat comb with a bump right at the back, if you can picture what I'm saying.