On a Windows Store App project im using the This method to send a email with an attachment, and it is working well but i would like to know if there is a way to define wich apps appear on the share list, for example i don't want the crossed apps to show. just the first one.
You can't do that. If you only want to send an e-mail you could call the e-mail app directly:
How to launch other apps https://msdn.microsoft.com/en-us/library/windows/apps/hh452690.aspx
Mailto syntax http://www.labnol.org/internet/email/learn-mailto-syntax/6748/