Feraligatr! It's so big and muscular and manly-like!
Meganium would be quite manly.
Also I got tired already with the Meganium thread so I'll just echo how it's just that people think fierce = male and stuff.
Though on their concept... while there were women in the samurai class, it was quite different. So I guess Samurott would count. On a similar take, Empoleon obviously uses emperor-like imagery.
In contrast, Serperior does it more gender-neutral. Though it's european royalty we are talking about.
As for masculine starters, I just can't see Blaziken as a female - even with the gender differences, Blaziken will always be rooster to me, and as far as I know, roosters are always males... I guess Samurott can also count, females with that kind of beard are rare or non-existent. As for Emboar, I think it could pass for a female because I can see the beard as a scarf of sorts with a little effort.
I'd have to go with Blaziken. A lot of them look very masculine, come to think of it.
Blastoise. He's got cannons comming out of his back. What else is there to say!?!