x3 on Junebuggena's post
To be certain at hatch, you need an autosexing breed or hybrid sex links.
I second a good quality Welsummer. Although one I had was somewhat noisy, overall mine have been large hens and good layers of darker eggs (depending on line). As chicks, the girls have heavy eyeliner and clear crisp head triangle with the stripe going all the way down the head, down the neck, all the way to the tail without any break. Males have very faint eyeliner, blotchy head, and the stripe breaks at the neck.
Another thought is Rhodebar. With this autosexing breed, the girl chicks are chipmunk and the boys are more brownish overall with a white dot on the head at hatch. Do not purchase a yellow gold chick...those are "wheaten" throwbacks and can be either male or female as the head dot is too hard to see against the gold. My Rhodebars are a very pleasing size and good layers of large tan eggs. Many lines have RIR infused to make for better layers. You would have to buy Rhodebars from a reputable breeder.
Some Barnevelder lines are almost auto-sexing if the breeder has been very careful. There is a difference in the chest color...I think the boys are white while the girls cream (or I may have that reversed)...but Barnevelder is not reliably auto-sexing in general. Barnevelders are a really nice size bird, very sweet tempered, and good layers of darker, red eggs.
Then it would be the sex link hybrids...Red Stars/Red Sexlinks/Cinnamon Queens/Red Stars/Gold Stars/ISA Browns....there are a lot of different names. The female chicks are fox red, or gold with fox red blush on head and backs, while the boys are pale yellow. My RSL's are my best production layers of beautiful terra cotta eggs. RSL's can vary between medium and large. As hens they have a lovely red with white lacing at hackles and often tail.
The black version is the Black Sexlinks. As chicks the girls are solid black and the boys black with white head dot. I really have enjoyed my BSL's. They are a medium to medium-large size bird, very sweet, curious, personable, and great layers of brown eggs. As hens, they will be black with red highlights varying at neck and chest.
Edited by Lady of McCamley - 1/6/16 at 9:17pm