Rescue dogs would always be my first choice but you asked for breeds so...
our family german shepherd was a fantastic dog. Super intelligent, very protective and a beautiful beautiful animal.
but, the samoyed we had before her was something special. She was damn near human in the way she'd reason things out. The shepherd was very sharp, no doubt, but the Sammy would have run rings around her, mentally. Spooky smart. The coat was a pain in summer though.