We have a blue mark collie who has the loveliest nature, caring, loves a fuss, follows my husband around like a shadow, warns away other dogs from our neurotic spaniel, but bless him wasn't the first in line when brain's were handed out! He is also a terror at grabbing the post out of the letter box leaving teeth marks in the envelopes.
He is also bigger than a border and very protective of house and occupants until he has been introduced although fine with people away from the house, and my younger son has not forgotten being pinned against the wall when he came down the stairs before being introduced properly - they are excellent friends now! The collie stare though - that's quite something.